JERUSALEM - Israel sought to persuade Syrian President Bashar Assad on Monday that its recent airstrikes around Damascus did not aim to weaken him in the face of a more than two-year-old rebellion.

Officials say Israel is reluctant to take sides in Syria's civil war for fear its actions would boost Islamists who are even more hostile to Israel than the Assad family, which has maintained a stable standoff with the Jewish state for decades.

But Israel has repeatedly warned it will not let Assad's ally Hezbollah receive hi-tech weaponry. Intelligence sources said Israel attacked Iranian-supplied missiles stored near the Syrian capital on Friday and Sunday that were awaiting transfer to Hezbollah guerrilla group in neighboring Lebanon.

Syria accused Israel of belligerence meant to shore up the outgunned anti-Assad rebels - drawing a denial on Monday from veteran Israeli lawmaker Tzachi Hanegbi, a confidant of Prime Minister Benjamin Netanyahu.

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Interviewed on Israel Radio, Hanegbi said the Netanyahu government aimed to avoid "an increase in tension with Syria by making clear that if there is activity, it is only against Hezbollah, not against the Syrian regime."

Hanegbi noted Israel had not formally acknowledged carrying out the raids in an effort to allow Assad to save face, adding that Netanyahu began a scheduled visit to China on Sunday to signal the sense of business as usual.

The Assad government has condemned the airstrikes as tantamount to a "declaration of war" and threatened unspecified retaliation.

But Hanegbi said Israel was ready for any development if the Syrians misinterpreted its messages and was ready "to respond harshly if indeed there is aggression against us".

As a precaution, Israel deployed two of its five Iron Dome rocket interceptors near the Syrian and Lebanese fronts and grounded civilian aircraft in the area, although an Israeli military spokesman said the airspace would reopen on Monday.

Military analysts say Syria would be no match for Israel in any confrontation. But Damascus, with its leverage over Hezbollah, could still consider proxy attacks through Lebanon, where Israel's conventional forces fought an inconclusive war against the Iranian-backed guerrillas in 2006.

Related:

• Israel strikes Syrian military research center, US official says
• Analysis: Israel may be ready for more active military role in Syria
• Full Syria coverage from NBC News

This story was originally published on Mon May 6, 2013 4:22 AM EDT

Israeli jets bombed a military research facility north of Damascus early Sunday, a senior official told NBC News. It marked the second Israeli attack on targets in Syria in recent days. 

Heavy explosions shook the city, and video shot by activists showed a fireball rising into the sky after Sunday's strikes.

Reuters reported that a Western intelligence source said the operation hit Iranian-supplied missiles that were en route to the Hezbollah militia in Lebanon.

A rebel spokesman, who spoke from a “liberated area” held by the opposition in Damascus, told NBC News there were huge explosions just before 2 a.m. Sunday local time (7 p.m. Saturday ET) in the Qaysoun mountains on the edge of Damascus. 

“Around 10 locations were hit," the spokesman said. "It was difficult to tell what was hit in the raid and what exploded afterwards.  Some of the targets were weapons and weapons depots.

"Secondary explosions continued for about four hours.  They shook all of Damascus. There was still smoke in the air as the sun came up.”

From its Damascus media office, the Free Syrian Army listed nine apparent targets, including the Syrian Revolutionary Guard, the 104th brigade headquarters, a weapons depot in Qasyoun and a military research center at Jamraya.

The FSA said power was cut in parts of Damascus at 1:48 am local time Sunday (6:48 p.m. Saturday ET). A FSA spokesman said the fires and explosions "made Damascus look like the day at night."

The White House said there would be no official comment on the latest attack, but diplomatic sources and U.S. officials told NBC News that the administration is fully supportive of the airstrikes.

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United Nations Secretary General Ban Ki-moon said he spoke with the head of the Arab League, Nabil ElAraby, about the Israeli air strikes on Sunday and expressed "grave concern" for the risks to regional security. 

On Friday, Israeli warplanes launched strikes against targets inside Syria, U.S. officials told NBC News. It’s believed the primary target also was a shipment of weapons headed for Hezbollah, they said. A senior U.S. official said the airstrikes were believed to be related to delivery systems for chemical weapons.

After that attack, an Israeli spokesman in Washington said that Israel would not comment specifically on the reports but said that “Israel is determined to prevent the transfer of chemical weapons or other game-changing weaponry by the Syrian regime to terrorists, especially to Hezbollah in Lebanon.”

It wasn’t clear whether the Israelis alerted the U.S. before the attack. White House officials referred all questions to the Israelis.

Rebel units were in disagreement about what type of weapons were in the convoy, Reuters reported. A rebel from an information-gathering unit in Damascus that calls itself "The Syrian Islamic Masts Intelligence" said the convoy carried anti-aircraft missiles.

The rebel, who asked not to be named, added: "There were three strikes by Israeli F-16 jets that damaged a convoy carrying anti-aircraft missiles heading to the Shi'ite Lebanese party (Hezbollah) along the Damascus-Beirut military road. One strike hit a site near the (Syrian) Fourth Armoured Division in al-Saboura but we have been unable to determine what is in that location."

However, Qassim Saadedine, a commander and spokesman for the rebel Free Syrian Army, told Reuters he did not think the weapons were anti-aircraft. "We have nothing confirmed yet but we are assuming that it is some type of long-range missile that would be capable of carrying chemical materials," he said. 

In the January attack, Israeli fighter jets struck a convoy of sophisticated anti-aircraft missiles believed on their way to Hezbollah.  

Israeli Defense Minister Moshe Ya’alon publicly acknowledged the January airstrike inside Syria in a joint press conference with Defense Secretary Chuck Hagel in Tel Aviv on April 22. Ya’alon said any Syrian delivery of sophisticated weapons to rogue elements like Hezbollah would be a “red line” for Israel and “when they crossed this red line, we operated. We acted.”

MSNBC - TV

Syria is in the middle of a civil war pitting rebels against the regime of President Bashir Assad. Tens of thousands have already died, and the possible use of the nation’s stockpile of chemical weapons has been of grave concern to the U.S. and other nations.

Last week, the White House said there was evidence that Syria’s government may have used chemical weapons against its own people. But President Barack Obama has cautioned against rushing to action against Assad’s government, saying that the U.S. required more evidence before getting involved in the civil war there.  

The U.S. has long believed that Syria was stockpiling chemical weapons. Intelligence reports indicate that it has sarin and the nerve agent tabun along with traditional chemicals like mustard gas and hydrogen cyanide. A 2011 CIA report said Syria was also developing the potent nerve agent VX, which could render a city uninhabitable for days.

Syria has said that it hasn’t used and will not use chemical weapons.

On Tuesday, Hezbollah’s leader warned the rebels that his militia was ready to intervene on Assad’s side in Syria’s civil war. There have been concerns that Syrian SCUD missiles that might be capable of carrying chemical weapons could be transferred to Hezbollah.

NBC News' Richard Engel, Kristen Welker and Stacey Klein and Reuters contributed to this report.

Related:

• Israel to Syria's Assad: Airstrikes not aimed at helping rebels
• Syrian government used chemical weapons 4 times, rebels say

This story was originally published on Sun May 5, 2013 10:33 AM EDT

NEWS ANALYSIS

ANTAKYA, Turkey -- War makes strange bedfellows. President Bashar Assad’s regime is in the unique position of being targeted both by Israel and supporters of al Qaeda.

It is hard to imagine more a diverse couple: Sworn enemies fighting against the same government.

Israel carried out a series of attacks on military targets in Damascus early Sunday, close to President Assad’s main compound, US officials told NBC News. A rebel spokesman said about 10 locations had been hit, adding: “They shook all of Damascus. There was still smoke in the air as the sun came up.”

Witnesses said they heard low-flying jets in the air, but only after the explosions began.  Witnesses also claim to have heard jets in Lebanon shortly before the raid.  Israel has not confirmed it carried out any attack.

Syrian state TV blamed Israel, and said it was helping the rebels it calls terrorists.

An Israeli source said Sunday’s targets included Iranian-made missiles bound for Hezbollah.

The rebel spokesman in Damascus said the rebels’ “spirits were lifted” by the pre-dawn raid, and that they resumed “intense attacks” on the regime in the capital on Sunday morning.

While there is no evidence that Israel is coordinating with the Syrian opposition, both are worried about what could happen as the civil war spins further out of control.

Israel specifically does not want Syria to hand over weapons, chemical or conventional, to Hezbollah.

Both Hezbollah – which is based in Lebanon, just north of Israel - and Iran are allies of Bashar Assad.

Israel and Hezbollah fought a bloody war in 2006.  But Israel doesn’t fully back the rebels either, especially not a powerful contingent of Islamic radicals. 

Israel does not want the Nusra front, which has pledged allegiance to al Qaeda, to obtain chemical weapons.  Neither does Washington.  Israel’s strategy thus far appears to be targeting threats as they come up and picking them off. 

If Israel sees weapons moving toward its border, it acts.  But many across the region are now wondering if this raid, larger in scale, is the start of a more active Israeli military role.  Has Israel decided that the longer the conflict drags on, the more risks there are regional stability?  Was this another surgical strike or the start of a new policy?  The answer may become clear in the coming days.

Related video: Syrian government used chemical weapons 4 times, rebels say

Ammar Cheikhomar / NBC News

The Old Market in Antakya, Turkey, has become a frequent stop for jihadists on their way to or from Syria, where they are battling the regime of President Bashar Assad.

ANTAKYA, Turkey -- In the Old Market of the ancient city of Antakya, there is a palpable sense of unease.

For wandering among the ordinary shoppers and tourists drawn to this border town -- known in antiquity as Antioch -- are hardened fighters like Abu Muntaser Alliby.

“I wish to die in Syria while I'm defending the oppressed there,” said the 27-year-old Islamist fighter from Libya, a veteran of three six-week tours in Syria who adopted a false name when he took up arms.

Antakya has gone from a tranquil stop on the tourist trail sometimes called "Tuscany with minarets" to a key staging post for the thousands of foreign fighters who have flocked to wage jihad against President Bashar Assad in Syria, bolstering the ranks of al Qaeda and Taliban-style militias.

The presence of Alliby and others like him has sparked angry protests by local people in the city. But others have profited, with shops springing up to supply the new demand for camouflage clothing, communication devices, backpacks and other equipment.

Their presence has also created a headache for the rebel Free Syrian Army. While they are allies in the struggle to topple Assad, their goal of establishing one Islamist state covering the entire Arab region is far removed from the FSA’s hopes of a democratic Syria.

And they are also cited as the main reason why the U.S. and other Western countries have not supplied the rebels with arms -- as some may end up in the hands of Alliby and his comrades.

Some analysts now believe this policy has inadvertently helped groups like Jabhat al-Nusra -- officially allied with al Qaeda in Iraq -- and the Syrian Islamic Front, an umbrella body of disparate groups with a similar ideology to the Taliban. At the moment, they're the only ones getting a steady stream of money and weapons and therefore are more attractive to would-be fighters than the poorly armed FSA.

But, listening to Alliby, it’s easy to see why the Obama administration is nervous and Israel might decide to take military action.

“We all have the same goal, which is to bring down the Syrian infidel regime and raise the banner ‘no God but Allah’ in Syria,” he said as he looked through the market for a backpack.

Ammar Cheikhomar / NBC News

The Old Market in picturesque Antakya has become a haunt for jihadists on their way to or from Syria. Many in the town are upset by their presence, but the fighters are buying, so vendors are selling.

“I guess that this is  the goal of every Muslim in Syria. ... We are all Muslims and we all ask for the jihad and hope to die while we are defending our religion,” he said. “I said goodbye to my parents and friends. I don't want to go back. I hope that I die in Syria or in Palestine.”

“I think any mujahed [jihadi] in Islam wishes to fight in Palestine against the Jews,” he added. “And I hope that we can have a center of Muslim mujahedeen [holy warriors] in Syria to proceed from Syria to liberate Palestine. Jihad starts from Syria and ends in Jerusalem.”

Alliby, who said he fought in Libya during the revolt against Moammar Gadhafi during which one of his brothers was killed, added that while the Libyan dictator was bad, Assad was significantly worse.

“He is not a man; he is a monster who doesn't know the meaning of humanity and doesn't respect anyone in his dirty war -- not the young, not the old, no woman and no child,” he said. “We see what is happening daily in Syria and how the people suffer there. I mean killing and destruction and displacement.”

Alliby said he was a member of a jihadist Islamist organization. He refused to name the group, but he was unusually open. Most jihadists refuse point-blank to speak to Western media.

In addition to jihadists, Antakya has also drawn journalists from around the world. One hotel is known as the BBC’s base, another is home to al-Jazeera. The jihadists, too, have their favorite hotel at a discreet distance from media camps.

It is at the bargain end of the market, but -- unlike the cheapest establishments -- provides an Internet connection and breakfast.

The Free Syrian Army might not run to such luxuries. Its fighters literally count their bullets and struggle to buy equipment in marked contrast to the well-funded, well-armed Islamist groups.

Luay Mukdad, political and media coordinator for the Free Syrian Army, admitted some FSA groups were “short on weapons, short on money and communications, so that’s what’s forced them to cooperate” with extremist fighters.

“Let me be honest, as long as Jabhat al-Nusra is holding their ground against Bashar Assad, there’s no problem,” he said.

Al-Nusra was designated as a terrorist organization by the U.S. in December and formally announced its alliance with al Qaeda in Iraq last month.

Mukdad said the Islamists fighters’ strength had been exaggerated in the media, but he warned that unless the West helped the FSA they would become stronger and more dangerous -- for Syria and the Middle East. While the Islamists hate the West and shun their support, the FSA believes it cannot win without its aid.

Ammar Cheikhomar / NBC News

Though angry protests have sprung up against Islamist fighters stopping in Antakya, so have shops to supply the new demand for camouflage clothing, communication devices, backpacks and other equipment used in war.

“We want Syria to be a civil country and we want to build our democracy,” he said, envisioning a country with “respect for all people” after the downfall of Assad.

Mukdad said the FSA would not allow extremists to take over the country.

“If Jabhat al-Nusra choose to be like al Qaeda or something and start trying to force people to do all the extremist things, like to force … the girls to put on the hijab or to do anything, the Free Syrian Army will protect the Syrian people,” he said. “Make us stronger. We want to protect our country and not let these people steal our future.”

Nadim Shehadi, a Middle East expert at the U.K.-based Chatham House think tank, said the best solution to the civil war would be an international military intervention, but he accepted that was not going to happen. The second-best option was arming the FSA, he said.

“What’s pushing people to join the jihadists is they are well-funded, well organized and they have the weapons,” he said. “They get them from private sources in the Gulf mainly. The others [non jihadist groups], they have to count their bullets.”

But Shehadi said that most ordinary Syrians now believed that the U.S. was on their side and the idea of Taliban-style rule was “not something that would fly” in ethnically diverse Syria.

“America used to be unpopular on the Arab street, when it used to support dictators. What’s emerging now is … an indication of American soft power,” he said. “[Syrians] want to be more like America than they want to be like Iran, Gaza or North Korea.”

Ammar Cheikhomar / NBC News

Vendors at the Old Market have found that jihadists coming in and out of Syria can be good customers. The militants are generally well funded compared with mainstream rebel forces.

Professor Peter Neumann, director of the International Centre for the Study of Radicalisation and Police Violence at King's College London, carried out a study that estimated there were 5,500 foreign fighters in Syria, most from the Middle East and North Africa.

Like Mukdad and Shehadi, he said the West should arm the FSA to provide a counter to the hard-line Islamist or Salafist groups and accept this would mean some weapons would fall into their hands.

"We're so afraid of funding the wrong people ... but the absence of our funding has actually made that more likely because the only money that comes through right now is this hard-core Islamist money," Neumann said.

He added, however, that all was not what it seemed in Syria.

"There has been in the past a huge incentive [for commanders] to pretend they are Salafist in order to get some weapons," he said. "There are perfectly secular commanders who've grown beards and who are flying the black flag of Islam on YouTube just in order to qualify for funding from Kuwait."

Ian Johnston reported from London.

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Full Syria coverage from NBC News

Baz Ratner / Reuters file

Mount Hermon is seen in the background as Israeli soldiers travel on mobile artillery units after an exercise on the Israeli-occupied Golan Heights on February 14. Israel is worried that the Golan, which it captured from Syria in 1967, will become a springboard for attacks targeting Israelis by jihadists who are taking part in the armed struggle against Syrian President Bashar Assad.

News analysis

TEL AVIV – About 2,000 Israeli army reservists were woken in the middle of the night this week and instructed by recorded announcement to report immediately to the northern border with Syria. They raced there, armed for war, only to discover it was a drill – Israel's largest in the north for years.

Every day, Israeli military leaders say, is a day in which peace could turn to war, especially in the north. Israeli army Chief of Staff Lt. Gen. Benny Gantz warned last month that Israel's border with Syria, its most stable border since the two countries signed their disengagement agreement 40 years ago, could explode at any moment.

"We are commemorating the 40th anniversary of the Yom Kippur War, and the years of quiet and stability are disappearing," he said at meeting at Israel's Institute for National Security Studies think tank, choosing his words carefully. "Instability (on the Golan Heights) is increasing."

Israel conquered the Golan Heights in the 1967 Six-Day War and later annexed it, a move not recognized by the international community which considers it to be occupied territory. Today, 44,000 people live on the Golan Heights and a United Nations force is stationed in a buffer zone between Israel and Syria. 

Israel has warned it will do whatever is necessary to prevent the Syrian government's large stockpile of chemical and biological weapons from falling into the hands of militants, believing that one day they may be used against Israel. It would be better, Israeli leaders believe, to fight in Syria against Islamists armed with non-conventional weapons than wait for them to attack Israel with them.

According to army sources quoted in the Maariv newspaper, Israel is sending fresh troops to man forward bases that have not been used for years because it was so quiet. The roads to the bases will also be paved and improved, the paper said.

Bullets and rockets have been fired from Syria into Israel at least a dozen times this year. Most are believed to be errant fire from fighting on the other side of the border, but the army says it sometimes comes from bunkers abandoned by the Syrian army, which pulled out to defend President Bashar Assad's regime in Damascus.

That vacuum along the border has been filled by Islamist militias – especially the al-Nusra front which says it is allied with al Qaeda – who repeatedly say their goal after toppling Assad is to use his territory as a launch-pad for attacks against Israel.

Israel has a history of short, sharp, specific attacks when its interests are threatened. In September 2007, Israel destroyed Syria's al-Kibar nuclear facility with a single devastating air attack. Earlier this year, Israel destroyed a truck convoy allegedly transporting strategic weapons from Syria to Hezbollah in Lebanon.

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But the prospect of Israeli soldiers operating on the ground in Syria, even if to protect Israel's interests, is at the very bottom of Israel's agenda, according to military analysts and politicians alike.

From a high point overlooking Israel's border near the Syrian town of Quneitra, abandoned and heavily damaged during the 1973 war, there is little sign of tension for now. The United Nations base for 1,000 international peacekeepers whose job is to patrol the buffer zone between Israel and Syria, showed no sign of activity during a two-hour visit this week. Not one vehicle entered or left the base.

It sits on the Israeli side of a new hi-tech razor fence that Israel built along its 50-mile border with Syria to keep the Syrian conflict from spilling into Israel. It is designed to keep out Syrians seeking refuge, militiamen seeking to attack Israeli targets, and above all, to keep Israel from intervening in Syria's civil war.

But the longer the bloody conflict lasts, Israeli military analysts warn, the more likely Israel will be dragged in.

Martin Fletcher is the author of "The List", "Breaking News" and "Walking Israel."

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• Israel becomes a fortress nation as it walls itself off from the Arab Spring
• Full Israel coverage on NBCNews.com

This story was originally published on Thu May 2, 2013 5:09 AM EDT

Bilal Hussein / AP

Pro-Syrian-government fighters from Lebanon stand guard at the border of the two countries on April 12. The head of Lebanon-based Hezbollah has threatened that his heavily armed group, backed by Iran, may become further involved in the battle against forces trying to topple Syrian President Bashar Assad.

BEIRUT -- The leader of Lebanon's Hezbollah militant group said Tuesday that Syrian rebels will not be able to defeat President Bashar Assad's regime militarily, warning that Syria's "real friends," including his Iranian-backed militant group, were ready to intervene on the government's side.

Hezbollah, a powerful Shiite Muslim group, is known to back Syrian regime fighters in Shiite villages near the Lebanon border against the mostly Sunni rebels fighting to topple Assad. The comments by Sheik Hassan Nasrallah were the strongest indication yet that his group was ready to get far more involved to rescue Assad's embattled regime.

"You will not be able to take Damascus by force and you will not be able to topple the regime militarily. This is a long battle," Nasrallah said, addressing the Syrian opposition.

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"Syria has real friends in the region and in the world who will not allow Syria to fall into the hands of America or Israel."

Hezbollah and Iran are close allies of Assad. Rebels have accused them of sending fighters to assist Syrian troops trying to crush the two-year-old anti-Assad uprising, which the U.N. says has killed more than 70,000 people.

Deeper and more overt Hezbollah involvement in the Syrian conflict is almost certain to threaten stability in Lebanon, which is sharply split along sectarian lines, and between supporters and opponents of Assad. It also risks drawing in Israel and Iran into a wider Middle East war.

Nasrallah said Tuesday there are no Iranian forces in Syria now, except for some experts who he said have been in Syria for decades. But he added: "What do you imagine would happen in the future if things deteriorate in a way that requires the intervention of the forces of resistance in this battle?"

Hezbollah has an arsenal that makes the group the most powerful military force in Lebanon, stronger than the national army. Its growing involvement in the Syrian civil war is already raising tensions inside the divided country and has drawn threats from enraged Syrian rebels and militants.

Nasrallah also said his fighters had a duty to protect the holy Shiite shrine of Sayida Zeinab, named for the granddaughter of Islam's Prophet Muhammad and located south of Damascus.

He said rebels have captured several villages around the shrine and have threatened to destroy it.

"If the shrine is destroyed things will get out of control," Nasrallah said, citing the 2006 bombing of the Shiite al-Askari shrine in the Iraqi city of Samarra. That attack was blamed on al Qaeda in Iraq and set off years of retaliatory bloodshed between Sunni and Shiite extremists that left thousands of Iraqis dead and pushed the country to the brink of civil war.

In recent weeks, government troops have overrun two rebel-held Damascus suburbs and a town outside the capital. They also have captured several villages near the border with Lebanon as part of their efforts to secure the strategic corridor running from Damascus to the Mediterranean coast, which is the heartland of the president's Alawite sect, an offshoot of Shiite Islam.

Related:

• Obama: 'Some evidence' Syria used chemical weapons
• Bomb blast in Syria's capital kills at least 13
• 6 killed as bomb targets Syria's prime minister

The specter of the bogus claims that former Iraqi dictator Saddam Hussein was hiding weapons of mass destruction — used to justify war —  hangs over the debate on how world leaders will respond to the possibility that Syria deployed chemical weapons.

Obama administration officials say they know they have to deal with the Iraq WMD legacy and will need definitive proof to persuade Russia, Syria’s only remaining ally in the U.N. Security Council, that Bashir Assad’s regime used deadly sarin gas against the opposition in the country’s bloody two-year civil war.

One senior U.S. defense official told reporters Thursday, "We have seen very bad movies before" — referring to previous instances where initial intelligence was proven wrong.

President Barack Obama has called the use of chemical weapons by Assad, a "red line" that if crossed would be a "game-changer" in the U.S. response to Syrian aggression.

The White House said Thursday that the U.S. believes "with some degree of varying confidence" that the Syrian government has used chemical weapons — specifically the nerve agent sarin — against its own people.

A letter from the White House to members of Congress said the assessment was based on "physiological samples" but called for a United Nations probe to corroborate it and nail down when and how they were used.

"We are continuing to do further work to establish a definitive judgment as to whether or not the red line has been crossed and to inform our decision-making about what we'll do next," a White House official said.

"All options are on the table in terms of our response," the official added.

U.S. intelligence agencies say that blood samples from two attacks last month in Aleppo tested positive for sarin.

Still, those sources say there is “no absolute proof” deadly agents were deployed by Assad's troops.

Administration sources tell NBC News they still have not been able to connect all the dots to prove who actually used the chemical weapons, whom they used them against, or when or where they were used. 

Secretary of State John Kerry discussed Syria with his Russian counterpart in Brussels last week, but the Russians remain unpersuaded to take action against the Syrian government, and the international community is demanding hard evidence to prove Syria is using chemical agents.

The proof, however, could be difficult to obtain.

A spokesman for UN Secretary-General Ban Ki-moon, who said that the United Nations can't take action based on intelligence from one country, said a team of experts assembled to investigate chemical weapons in Syria remains "grounded" in Cyprus because the Assad regime has blocked it from entering the country.

The U.N. has repeatedly called on Syria to let its inspection team in.

"The fact-finding team is on standby and ready to deploy in 24-48 hours," the U.N. spokesman said. 

Syria's information minister, Omran al-Zoubi, said in an interview with Russian TV that the government has not and will not use chemical weapons and blamed potential evidence of their existence on "armed terrorist groups," the state news agency reported.

The chemical weapons investigation and counterclaims recall the experience in Iraq, where U.N. inspection teams were hampered in their effort to find weapons of mass destruction amid U.S. intelligence reports suggesting they were being hidden by Saddam.

It was the alleged existence of the so-called WMD the George W. Bush administration used to justify war in Iraq.

Despite a massive search by U.S. forces, no weapons of mass destruction ever turned up.

Sen. John McCain, R.-Ariz.,  was swift to react to the latest reports that Syria used chemical weapons, saying, “I think it's pretty obvious that red line has been crossed." He said the administration should now consider a military approach in Syria he has been advocating for two years that falls short of boots on the ground.

“That is to provide a safe area for the opposition to operate and  to establish a no-fly zone and provide weapons to the people in the resistance who we trust,” McCain said.

A White House official called for a high level of scrutiny, but also caution.

"Given our own history with intelligence assessments, including intelligence assessments related to weapons of mass destruction, it's very important that we are able to establish this with certainty and that we are able to present information in a way that is airtight," the official said.

Reuters contributed to this report.

Related: White House: US believes Syrian regime used chemical weapons

President Barack Obama said Tuesday that the United States has evidence that chemical weapons were used in Syria’s brutal civil war but that it remains unclear who used them.

In a White House press conference, Obama said there is “some evidence” that the regime of Syrian President Bashar Assad used the weapons, but urged against rushing to judgment, saying more facts must be known before any action taken.

“We don't know how they were used, when they were used, who used them," the president said, adding "we don't have a chain of custody that establishes what exactly happened."

He reiterated that the administration needs more intelligence before before he’s willing to entertain any kind of escalation in Syria.

“When I am making decisions about America’s national security and the potential for taking additional action in terms of chemical weapons use, I’ve got to make sure I’ve got the facts,” he said.

As in the past, Obama referred to chemical weapons use as a “game-changer.” He gave no indication, however, that the United States or its allies would step up action against the Assad regime, adding that as long ago as last year he had asked the Pentagon to prepare options on Syria. Obama declined to elaborate on any plans in the works.

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“By ‘game-changer’ I mean that we would have to rethink the range of options that are available to us,” he said.

“Obviously, there are options … that are on the shelf right now that we have not deployed,” the president added.

Obama's caution about launching any military action against Syria in the absence of firm evidence of the use of chemical weapons likely stems from his predecessor, President George W. Bush, who has been criticized for starting the Iraq war over claims of weapons of mass destruction that never materialized.

"If we end up rushing to judgment without hard, effective evidence, then we can find ourselves in the position where we can't mobilize the international community to support what we do," he said.

The primary incident of alleged chemical weapons use came on March 19, when rebel and government forces were engaged in heavy fighting in a strategically important town near the city of Aleppo.

Syria’s state news agency SANA said 25 people were killed and dozens more were injured; they blamed the attack on rebels.

Rebel forces, meanwhile, said government forces had delivered a chemical agent with a Scud missile.

Both sides described civilians panicking, having breathing difficulties and convulsing, and both sides continue to blame each other.

Regional reaction
Countries in the region have been watching with growing concern at the worsening conflict in Syria, none more so than Israel. 

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People resisting the army of President Bashar al-Assad in northern Syria cope with loss and prepare for fighting.

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"The main risk for Israel is that chemical weapons end up in the hands of the Hezbollah or the hands of any jihadist," said Dr. David Friedman, a chemical and biological weapons expert at the Institute for National Security Studies in Tel Aviv. "If they do then all the world needs to be afraid of this."

Nonetheless, he said, Israel wasn't pressuring Obama to intervene in Syria.

Gamal Abdel Gawad, a political science professor at the American University in Cairo, said that Obama would likely not react with an all-out military intervention.  

"Its a good idea (not to intervene militarily). The risks are very high," he said.  "Rule number one in military intervention is to know how to get out. There is no answer to this question. You are playing with adversaries that have a lot of potential and resources."

Obama’s comments came on a day when a bombing in central Damascus killed at least 13 people and injured scores more, according to state media and the Britain-based Human Rights Watch.

Syria’s two-year civil war has claimed more than 70,000 lives, according to the United Nations.

The U.S. and other countries have provided aid to rebels but have stopped short of committing to further involvement in the battle to overthrow Assad.

NBC News's Paul Goldman and Charlene Gubash contributed to this report. 

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Obama cautions against rush to action in Syria

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This story was originally published on Tue Apr 30, 2013 11:48 AM EDT

Khaled al-Hariri / Reuters

A destroyed car is pictured near the former Interior Ministry building after a blast in central Damascus on Tuesday killed at least 13 people and injured dozens more, according to state television and activists.

BEIRUT -- A bomb in central Damascus killed 13 people on Tuesday, state television said, a day after Prime Minister Wael al-Halki survived an attack on his convoy in the heart of the Syrian capital.

State television said 70 people were wounded, several critically. The Britain-based Syrian Observatory for Human Rights reported that nine civilians and five soldiers had died.

Pro-government Al-Ikhbariya television showed firefighters running through thick smoke after the blast in Marjeh Square. Two bodies could be seen on the ground.

The target of the attack was not immediately clear. Footage showed the site of the blast was near the former Interior Ministry building on one of the capital's main roads.

Monday's attack on the prime minister's convoy killed six people in what has become an increasingly common tactic used by rebels.

A resident of Damascus, who lives a mile from the blast site, said the explosion shook the doors of her house.

"It must be huge for me to hear it like that. Casualties must be horrific because it is a super busy square at this time of day," she said over Skype.

Rebels have increased their attacks on Damascus, which include mortar fire from the contested suburbs, in a civil war that has cost more than 70,000 lives according to U.N. estimates.

A bomb in July killed four of President Bashar Assad's aides, including his brother-in-law Assef Shawkat and the defense minister.

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Syrian Prime Minister Wael al-Halki survived a bomb attack on his convoy in Damascus on Monday, state media and activists said, as rebels struck in the heart of President Bashar Assad's capital.

Six people were killed in the blast, the Britain-based Syrian Observatory for Human Rights said, the latest in a series of rebel attacks on government targets including a December bombing that wounded Assad's interior minister.

Halki wields little power, but the attack highlighted the rebels' growing ability to target symbols of Assad's authority in a civil war that has cost more than 70,000 lives, according to the United Nations.

AP

This photo released by the Syrian official news agency SANA shows firefighters extinguishing burning cars after a blast in the Mazzeh neighborhood of Damascus, Syria, on Monday.

Assad picked Halki in August to replace Riyadh Hijab, who defected and escaped to neighboring Jordan just weeks after a Damascus bombing killed four of the president's top security advisers.

In comments released by the state news agency SANA but not shown on television, Halki was quoted as condemning the attack as a sign of "bankruptcy and failure of the terrorist groups," a reference to the rebels battling to overthrow Assad.

The blast shook the Mezze district soon after 9 a.m. local time (2 a.m. ET) and sent thick black smoke into the sky. The Observatory said one man accompanying Halki was killed as well as five passers-by.

State television showed firemen hosing down the charred and mangled remains of a car. Nearby was a large white bus, its windows blown out and its seats gutted by fire. Glass and debris were scattered across several lanes of a main road.

"The terrorist explosion in al-Mezze was an attempt to target the convoy of the prime minister. Doctor Wael al-Halki is well and not hurt at all," state television said.

It later broadcast footage of Halki, who appeared composed and unruffled, chairing what it said was an economic committee.

Mezze is part of a shrinking "Square of Security" in central Damascus, where many government and military institutions are based and where senior Syrian officials live.

Sheltered for nearly two years from the bloodshed and destruction ravaging much of the rest of Syria, it has been slowly sucked into violence as rebel forces based to the east of the capital launch mortar attacks and carry out bombings in the center.

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• Fighting reported near suspected chemical weapons site in Syria
• Obama reiterates chemical weapons would be 'game-changer'
• Inside a Syrian city split between rival militias

This story was originally published on Mon Apr 29, 2013 4:37 AM EDT

President Obama said Friday that the potential use of chemical weapons by the ruling regime of Syria against its people “adds increased urgency” to international concern about the regime.

Speaking to reporters during an Oval Office meeting with King Abdullah of Jordan, Obama noted that reports of the use of chemical weapons by the Syrian government were preliminary. That information, he said, “does not tell us when they were used, how they were used.”

Still, the president said: “Obviously, horrific as it is when mortars are being fired on civilians and people are being indiscriminately killed, to use potential weapons of mass destruction on civilian populations crosses another line with respect to international norms and international law. And that is going to be a game-changer.”

On Tuesday, the Israeli military published intelligence findings that President Bashar Assad’s forces had used chemical weapons repeatedly in recent months. Part of Israel’s concern, and Obama’s, is that those weapons could fall into terrorist hands.

Two days later, Defense Secretary Chuck Hagel said that the U.S. believes “with some degree of varying confidence” that the Syrian government has used chemical weapons, specifically the nerve agent sarin, against its people.

A letter from the White House to Congress said the assessment was based on “physiological samples” but called for a United Nations probe to corroborate it and nail down when and how they were used.

The American response is shadowed by the legacy of flawed intelligence reports of weapons of mass destruction that led to the invasion of Iraq.

The president spoke after the deputy foreign minister of Israel said world powers may now conclude there was “no avoiding” action to take control of the Assad regime’s chemical stockpile.

British Prime Minister David Cameron also said there was limited but growing evidence that the Syrian regime had used chemical agents.

Echoing the administration’s caution, Rep. Dutch Ruppersberger of Maryland, the top Democrat on the House Intelligence Committee, said Friday that “every option is on the table” but stressed that “we want to do everything we can to avoid putting boots on the ground.”

Sen. John McCain, R.-Ariz., said on Thursday that the Obama administration should consider a military approach but not commit American troops. He suggested providing weapons to trusted parts of the Syrian resistance.

The uprising against Assad began in March 2011, and an estimated 70,000 people have been killed in the violence that has followed.

Slideshow: Syria uprising

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A look back at the conflict that has overtaken the country.

Launch slideshow

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This story was originally published on Fri Apr 26, 2013 8:02 AM EDT