Suhaib Salem / Pool via EPA

Hamas chief Khaled Meshaal shakes hands with supporters upon his arrival Friday at the Rafah crossing in the southern Gaza Strip.

CAIRO — The head of Hamas' political wing Khaled Mashaal entered the Gaza Strip Friday in an unprecedented move by the organization.

Mashaal, 56, is the head of Hamas' politburo-in-exile and the most senior Hamas figure in the entire organization.

He technically oversees the political wing and the military wing, known as the Al Qassam Brigades.

His visit to Gaza is his first to the Palestinian territories since 1967, when he left at the age of 11 as Israel occupied the West Bank, East Jerusalem and Gaza Strip in the Six-Day War.

Mashaal survived an assassination attempt in Jordan in 1997 that was embarrassing for Prime Minister Benjamin  Netanyahu — who was serving as premier in his first stint at the time — because the Mossad agents were caught.

Israel then had to give the Jordanians the antidote to the poison Mashaal was injected with.

Officials: Israel kills Hamas military chief, 7 others in airstrike

Significant step
Mashaal’s visit to Gaza is a significant step for two reasons.

First, it is a sign Hamas has confidence that the ceasefire with Israel is holding and that there will not be an assassination attempts during his visit.

Second, Hamas in recent years has seen political infighting between the organization’s exiled leadership and the internal one in Gaza and the West Bank. His visit is aimed at reconciling these differences.

After Gaza violence, Israel declares mission accomplished, Hamas claims victory

Mashaal says he is shielded by the international involvement in the ceasefire he negotiated.

"Israel always violates agreements but Israel will be condemned if it doesn't abide by this written agreement under Egyptian sponsorship and U.S. presence," he told Reuters last week, referring to the ceasefire deal, which stipulated ending targeted assassinations. "The world witnessed it.”

Mouin Rabbani, an expert on Palestinian affairs, summed up the Palestinian view of Mashaal's arrival.

"It is a very welcome poke in the eye of Israel," he told Reuters. "It is a significant visit that shows Israel's position in Gaza has further weakened to the extent that the leader of the organization it went to war with last month and it tried to murder can now visit Gaza with the trappings of an official visit." 

Reuters contributed to this report.

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Mohammed Salem / Reuters

Palestinians rest as a worker repairs a smuggling tunnel dug beneath the Egyptian-Gaza border in Rafah, in the southern Gaza Strip on Monday. Knee-deep in craters carved out by Israeli airstrikes, Palestinians wielded shovels and planks to reopen tunnels used to smuggle in goods from Egypt to Gaza, as international aid agencies raced to replenish Gaza's supplies.

Palestinians wielded shovels and planks Monday to reopen tunnels used to smuggle in goods from Egypt to the Gaza Strip after Israel's eight-day offensive against Hamas.

Israeli airstrikes have heavily targeted the network of tunnels, which smugglers use to bring in various items — including food, fuel, construction materials and weapons — to Gaza's 1.6 million residents.

Residents along the Egypt-Gaza border say that smugglers and tunnel owners are still inspecting the damage but that many of the tunnels still operate, though at reduced capacity, according to The Associated Press.

An Egyptian security official, speaking to the AP on condition of anonymity because he was not authorized to talk to the media, estimated that as of Sunday half the tunnels were not functioning.

PhotoBlog: Gazans work to reopen tunnels bombed by Israel

The tunnels were developed as a way for Palestinians in Gaza to sidestep Egyptian and Israeli restrictions.

Though technically illegal, the tunnels have until recently been tolerated to varying degrees on the Egyptian side of the border.

Lifeline
While many Gazans depend on the tunnels for basic food and supplies, the underground facilities have also been crucial to arming Hamas and other militant groups.

"You can smuggle weapons, have people going in and out," Benedetta Berti, a research fellow at the Institute for National Security Studies in Tel Aviv, recently told USA Today. "Security on the border and monitoring tunnels ... has to be done."

Slideshow: Israel and Gaza: 8 days of violence

Bernat Armangue / AP

Israel's military said it had accomplished its objectives while Hamas claimed victory after the two sides exchanged deadly airstrikes and rocket attacks for over a week.

Launch slideshow

According to an August report by the International Crisis Group, between $500-700 million in goods are estimated to pass through the tunnels each year. The Hamas government has charged a tax of around 14.5 percent since the beginning of 2012, the report said. In 2011 alone, 13,000 cars were estimated to have come through the tunnels.

Some smugglers have made a fortune off the smuggling.

"Eight hundred millionaires and 1,600 near-millionaires control the tunnels at the expense of both Egyptian and Palestinian national interests," Palestinian President Mahmoud Abbas, who leads the Palestinian Authority in the West Bank, told The Economist.

Thousands of other workers make a living transporting goods back and forth through the tunnels, reports say.

As of late 2010, around 1,000 tunnels were in operation along the border, the nonpartisan Congressional Research Service said in a report.

ANALYSIS: What Gaza crisis taught Israel about Iran

Hamas began a dramatic expansion off the tunneling network following Israel's 2005 withdrawal from the coastal territory, analysts say. The Islamist group, which Israel and the United States classify as a terrorist group, came to power in Gaza in 2007.

"Under the closure regime aimed at undermining Hamas's control over the territory, the tunneling network has become Gaza's primary economic engine and mode of rearmament for militants," the CRS report said.

The tunnels are believed to be of a relatively high quality of engineering and construction, with some including electricity, ventilation, intercoms, and a rail system, according to the report.

The Iran link
Many of the weapons smuggled into Gaza appear to have originated in Iran, experts say.

Iran's fingerprints on Hamas weaponry, but role in Israel-Gaza crisis murky

The Israeli military released footage earlier this month that it said showed that many of Hamas' weapons, such as the Fajr-5 missiles, came from Iran.

The Shiite-led government in Iran has found common cause with the Sunni Hamas over a mutual foe, Israel, but experts agree that its influence is often indirect.

Still, according to a 2009 cable obtained by WikiLeaks, Israeli intelligence told a U.S. official that Israel's air attacks on Gaza's tunnels were "part of a bigger campaign to address the main issue of Iranian support to Hamas."

For example, Israel said the Iranians had developed a version of the 122mm rocket specifically for Hamas: the weapon "came in four pieces that could fit through narrow tunnels and be reassembled in Gaza."

Despite troubles at home, Egypt's Morsi is pivotal player in Mideast

Israel has promised to ease its blockade on Gaza as part of a cease-fire last week that ended the intense fighting. But as negotiations inch forward, no timeline has yet been set for the lifting the restrictions.

Under its new Islamist government, Egypt has moved to reduce smuggling in the tunnel by sealing off the entrances on its side of the border.

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Egypt and Israel have blamed a recent surge in lawlessness on the Egyptian side of the Gaza border in large part to smuggling through the tunnels.

In August, the Egyptian army launched a crackdown on militants in the Sinai Peninsula after an attack killed 16 Egyptian police officers.

The Associated Press and Reuters contributed to this report.

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Updated at 3:02 p.m. ET: GAZA CITY, Gaza Strip -- The leader of Hamas said Monday it was up to Israel to end the new conflict it had started, adding that a "land war" would cost Israeli Prime Minister Benjamin Netanyahu the election.

"[Netanyahu] can do it, but he knows that it will not be a picnic and that it could be his political death and cost him the elections," Khaled Meshaal, exiled leader of Hamas, told a news conference in Cairo.

"Whoever started the war must end it," Meshaal said, adding that Netanyahu, who faces an election in January, had asked for a truce, an assertion a senior Israeli official described as untrue.

For its part, Israel said that while it was prepared to step up its offensive by sending in troops, it preferred a diplomatic solution that would end Palestinian rocket fire.

Israeli Vice Prime Minister Moshe Yaalon has said that "if there is quiet in the south and no rockets and missiles are fired at Israel's citizens, nor terrorist attacks engineered from the Gaza Strip, we will not attack."

According to a poll by Israel's Haaretz newspaper, 84 percent of Israelis supported the current Gaza assault, but only 30 percent wanted an invasion, while 19 percent wanted their government to work on securing a truce soon.

Acting as a mediator, Egypt said Monday that a deal for a truce to end the fighting could be close, as Israel bombed dozens of suspected guerrilla sites in the densely populated Hamas-ruled Gaza Strip in its campaign to quell militant rocket fire menacing nearly half of Israel's population.

Twelve Palestinian civilians and four fighters were killed in the sixth day of fighting, local officials said, raising the number of Palestinian dead to 101, the Hamas-run Health Ministry told Reuters, listing 24 children among them. Hospital officials in Gaza said more than half of those killed were non-combatants. Three Israeli civilians died on Thursday in a rocket strike and dozens others have been wounded.

Slideshow: Israel, Gaza violence escalates

Ammar Awad / Reuters

Two sides exchange deadly airstrikes, rocket attacks.

Launch slideshow

Among the targets struck in Gaza City Monday was the Al Shorouq media building, which Israeli warplanes hit for the second straight day. The attack targeted a second-floor apartment used by a leading Islamic Jihad militant. He was killed and four others were injured, NBC News' Ayman Mohyeldin reported.

The Israeli military said it targeted only the floor used by the militants. “The senior [Islamic Jihad] cadre was operating in a media building. They weren’t there to be interviewed. They were using reporters as human shields,” it said on Twitter.

But the lower floors of the building caught fire, trapping journalists on the higher levels. Firefighters were trying to put out the blaze and get the journalists out of the building. The Hamas TV station is located on the top floor.

Family mourned
Thousands turned out on Gaza's streets Monday to mourn four children and five women, who were among the 11 people killed in an Israeli strike that flattened a three-story home the previous day.

The bodies were wrapped in Palestinian and Hamas flags. Echoes of explosions mixed with cries of grief and defiant chants of "God is greatest."

Israel said it was investigating the strike that brought the home crashing down on the al-Dalu family, where the dead spanned four generations. Some Israeli newspapers said the wrong house may have been mistakenly targeted.

Since Wednesday, 877 rockets have been fired from Gaza toward Israel, the Israeli military said Monday. Of those, 570 rockets have struck Israel while the country’s air defense system has intercepted 307, according to the military. Forty-five rockets were fired at southern Israel on Monday, causing no casualties, police said.

Israel's decision to step up targeted attacks on leaders in Gaza on Sunday marked a new and risky phase of the operation, given the likelihood of civilian casualties in the crowded territory of 1.6 million Palestinians.

Negotiations inch forward
International efforts to wrest a cease-fire from the two sides has intensified despite the escalated hostilities. The failure to end the fighting could touch off an Israeli ground invasion, for which thousands of soldiers, backed by tanks and armored vehicles, have already been mobilized and dispatched to Gaza's border.

Leading cease-fire mediation efforts is Egypt, which borders both Israel and Gaza and whose Islamist-rooted government has been hosting leaders of Hamas.

“I strongly urge the parties to cooperate with all efforts led by Egypt to reach an immediate cease-fire," U.N. Secretary-General Ban Ki-moon said before leaving for Egypt. He visits Israel on Tuesday.

European Union governments also said they supported Egyptian efforts to mediate.

Related links:

Key players in the Israel-Gaza cross-border conflict

How Israel's 'Iron Dome' intercepts incoming rockets in Gaza conflict

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On Sunday, President Barack Obama said it would be "preferable" to avoid a move into Gaza, but that Israel had a right to self-defense and no country would tolerate missiles raining down on its citizens.

Egyptian Foreign Minister Mohamed Kamel Amr, Arab League chief Nabil Elaraby and several other Arab foreign ministers will visit Gaza on Tuesday to show solidarity with Palestinians. Turkish Foreign Minister Ahmet Davutoglu will accompany them, officials said.

Mohammed Saber / EPA

A Palestinian woman inspects the rubble of her destroyed house after an Israeli airstrike in the eastern part of Gaza City on Monday.

Forces gather
Israel launched the current offensive Wednesday after months of intensifying rocket fire from the Gaza Strip, which continued despite the strikes.

Israeli tanks, artillery and infantry have massed in field encampments along the sandy, fenced-off border and military convoys moved on roads in the area. Israel has also authorized the call-up of 75,000 military reservists, so far mobilizing around half that number.

Overnight, aircraft targeted about 80 militant sites, including underground rocket-launching sites, smuggling tunnels and training bases, as well as command posts and weapons storage facilities located in buildings owned by militant commanders, the military said Monday in a release.  

Aircraft and gunboats joined forces to attack police headquarters, and rocket squads were struck as they prepared to fire, the release said.

In all, more than 1,000 Gaza targets have been struck since the operation began.

Some Hamas rockets reached as far as Tel Aviv, Israel's commercial capital, but were shot down by the country's air defense system.

As a precaution against the rocket interceptions endangering nearby Ben-Gurion International Airport, civil aviation authorities said on Monday new flight paths were being used.

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Israel's declared goal is to deplete Gaza arsenals and force Hamas to stop rocket fire that has bedeviled Israeli border towns for years. The rockets now have greater range, putting Tel Aviv and Jerusalem within their reach -- a strategic weapon for Gaza's otherwise massively outgunned guerrillas.

Lior Mizrahi / Getty Images

Israeli soldiers prepare their weapons in a deployment area near the Gaza border on Monday.

NBC News' Ayman Mohyeldin, The Associated Press and Reuters contributed to this report.

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Updated at 11 p.m. ET: The day after Israeli aircraft bombed Hamas offices in Gaza and Hamas fired a rocket at Tel Aviv, Egypt's president said Saturday night that "some indications" exist that a ceasefire might be possible.

"There are some indications that there is a possibility of a ceasefire soon, but we do not yet have firm guarantees," Egyptian President Mohammed Morsi told a joint news conference with Turkish Prime Minister Tayyip Erdogan, who was visiting Cairo.

Egypt had brokered an informal truce in October that has since collapsed, and it has said it is working for a new deal.

Before dawn on Saturday, Israeli aircraft fired missiles at Gaza buildings that included the office of Gaza Prime Minister Ismail Haniyeh, as armed conflict in the region entered its fourth day.

Uriel Sinai / Getty Images

An Israeli missile from the "Iron Dome" defense system is fired Saturday to destroy a rocket fired from Gaza at Tel Aviv.

Hamas later retaliated, firing a rocket at Israel's biggest city, Tel Aviv, for the third straight day. Police said it was destroyed in mid-air by an Iron Dome anti-missile battery deployed hours earlier, and no one was injured.

But Hamas rocket fire appeared to be subsiding. The Israeli military said Sunday morning that Gaza militants hadn't attacked Israel since the night before.

Overnight, six journalists were wounded in Gaza City when Israeli warplanes hit a television station, according to Agence France-Presse. Reuters said witnesses identified the station as al Quds, which Israel sees as pro-Hamas. Sky News reported that around 5 a.m. local time, two missiles hit the building that houses its studios and offices. Al-Arabiya also said that its offices had been hit.

Medics say that 48 people living in Gaza were killed by early Sunday and more than 450 injured since Israel started airstrikes Wednesday, Agence France-Presse reported.

In the Israeli Mediterranean port of Ashdod, a rocket ripped into several balconies. Police said five people were hurt.

As the crisis escalates, Israel's military is considering waging a ground campaign. It started drafting 16,000 reserve troops on Friday, as Israel's Cabinet authorized the mobilization of up to 75,000 reservists. Troops were massing on the border and witnesses said they could see Israeli ships off Gaza's coast, NBC News' Ayman Mohyeldin reported.

In a broadcast statement, Hamas’s military wing, the Qassam Brigades, said a ground invasion would be "stupid and foolish."

The statement also said that Hamas has used sophisticated weapons – including locally made, long-range rockets -- to strike at Tel Aviv and Jerusalem.

Hamas says it blames Israel for the war, saying that Israeli leaders made “stupid” decisions that triggered the wrath of Hamas, and that has forced Israelis into bomb shelters.

Despite the violence, Tunisia's foreign minister arrived in the coastal enclave on Saturday in a show of solidarity, denouncing the Israeli attacks as illegitimate and unacceptable.

Officials in Gaza said 41 Palestinians, among them 20 civilians including eight children and a pregnant woman, had been killed in Gaza since Israel began operations four days ago. Three Israeli civilians were killed by a rocket on Thursday.

Israel's military said its air force had hit at least 180 targets since midnight, including a police headquarters, government buildings, rocket launching squads and a Hamas training facility in the impoverished territory.

Reporting from Gaza City, NBC's Richard Engel posted a message on Twitter describing the buzz of drones over the city. "It sounds like everyone is out mowing their lawns in the dark," he said.

A three-story house belonging to Hamas official Abu Hassan Salah was also hit and completely destroyed early on Saturday. Rescuers said at least 30 people were pulled from the rubble.

"What Israel is doing is not legitimate and is not acceptable at all," Tunisian Foreign Minister Rafik Abdesslem said as he visited Haniyeh's wrecked headquarters. "It does not have total immunity and is not above international law."

Hatem Moussa / AP

A ball of fire rises from an Israeli airstrike in Gaza City on Saturday.

Hamas says it is committed to continued confrontation with Israel and is eager not to seem any less resolute than smaller, more radical groups that have emerged in Gaza in recent years.

The Islamist Hamas has ruled Gaza since 2007. Israel pulled settlers out of Gaza in 2005 but has maintained a blockade of the territory.

Israel launched a massive air campaign on Wednesday with the declared aim of deterring Hamas from launching cross-border rocket salvoes that have plagued southern Israel for years.

The Palestinians have fired hundreds of rockets out of Gaza, including one at Jerusalem and three at Tel Aviv - Israel's commercial center. Jerusalem had not been targeted in such a way since 1970, and Tel Aviv since 1991.

Key players in the Israel-Gaza cross-border conflict

Although there were no reports of casualties or damage in either city, the long-range attacks came as a shock and advanced the prospect of an Israeli ground invasion into Gaza.

"This will last as long as is needed; we have not limited ourselves in means or in time," Foreign Minister Avigdor Lieberman told Israel's Channel One television on Saturday.

In a call with Israeli Prime Minister Benjamin Netanyahu on Friday, U.S. President Barack Obama reiterated American support for Israel to defend itself, Reuters reported. The two leaders also discussed options for "de-escalating" the situation, the White House said in a statement.

He also called Egypt's Morsi on Friday, and underscored his hope of restoring stability.

Rockets from Gaza fired on Tel Aviv and Jerusalem

Netanyahu held a four-hour strategy session late on Friday with a clutch of senior ministers on widening the military campaign, while other cabinet members were polled by telephone on increasing mobilization.

Political sources said they decided to more than double the current reserve troop quota set for the Gaza offensive to 75,000. It did not necessarily mean all would be called up.

Suhaib Salem / Reuters

Palestinians inspect the destroyed office building of Hamas Prime Minister Ismail Haniyeh in Gaza City on Saturday.

In a further sign Netanyahu might be clearing the way for a ground operation, Israel's armed forces decreed a highway leading to the territory and two roads bordering the enclave of 1.7 million Palestinians off-limits to civilian traffic.

NBC's Ayman Mohyeldin answers your questions about Israel-Gaza conflict

The Israeli military said some 367 rockets fired from Gaza had hit Israel since Wednesday and at least 222 more were intercepted by its Iron Dome anti-missile system.

The Israel Defense Force said Saturday that mortar fire from Gaza had damaged an electricity cable in the south of Israel. "As a result, power is out in areas of northern Gaza Strip," the IDF said in a message posted on Twitter.

Four Iron Domes were deployed initially and a fifth was rushed into action on Saturday, weeks ahead of schedule. The army said it was placed in the Tel Aviv area, showing Israel's concern for the safety of its heavily populated coastline.

Reuters contributed to this report.

Slideshow: Israel, Gaza violence escalates

Ammar Awad / Reuters

Two sides exchange deadly airstrikes, rocket attacks.

Launch slideshow

Israel said it struck targets in the Gaza Strip on Monday after Palestinian militants fired rockets at southern Israel in what they said was a response to an Israel airstrike that wounded two militants and eight bystanders.

Meanwhile, the Israeli newspaper Haaretz, citing The Associated Press, said the Israeli air force flew mock raids over southern Lebanon after a mysterious unmanned aircraft was shot down over Israel over the weekend.

An Iranian military official was quoted as saying Monday that the drone's incursion exposed the weakness of Israeli air defenses, but did not confirm or deny Israeli charges that Tehran and southern Lebanon-based Shiite militia group Hezbollah were behind it.

Jamaluddin Aberoumand, deputy coordinator for Iran's Islamic Revolutionary Guard Corps, said the incident indicated that Israel's Iron Dome anti-missile defense system "does not work and lacks the necessary capacity," Fars news agency reported.

The Iron Dome system, jointly funded with the United States, is designed to shoot down short-range guerrilla rockets, not slow-flying aircraft. It intercepted more than 80 percent of the targets it engaged in March when nearly 300 rockets and mortars were fired at southern Israel, the Pentagon said at the time.

The drone was first spotted above the Mediterranean near the Gaza Strip to the west of Israel, said military spokeswoman Avital Leibovich. An Israeli warplane shot it down above a forest near the occupied West Bank.

Israeli parliament member Miri Regev, a former chief spokesman of the military, wrote on Twitter it was an "Iranian drone launched by Hezbollah."

Israeli defense officials have not confirmed the charge.

On at least one occasion, Iranian-backed Hezbollah has sent a drone into Israeli airspace. Also, in 2010, an Israeli warplane shot down an apparently unmanned balloon in the Negev near the country's Dimona nuclear reactor.

More Middle East & North African coverage on NBCNews.com

Sunday's flyover by Israeli jets appeared intended to demonstrate to Hezbollah that Israel retained air superiority, according to the AP.

On Monday, the Israeli army said it had targeted "Hamas terror activity sites and terrorist squads responsible for the rocket fire"in Gaza, but gave no details.

Gaza hospital officials said one Islamic Jihad militant thought to have been involved in the rocket attack had been wounded by Israeli tank fire east of the town of Rafah.

Residents of the town of Khan Younis in the southern Gaza Strip said an Israeli tank fired at the suspected launch area, slightly wounding four children and damaging a mosque minaret and a water tower.

The Israeli army says 470 rockets have been fired from Gaza this year, 10 in October alone.

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The armed wing of Hamas, the Palestinian Islamist faction that controls the Gaza Strip, said it had carried out the latest rocket attack with the militant Islamic Jihad group.

It was the first time since June that Hamas had acknowledged launching rockets at Israel.

An Israeli military spokeswoman said some rockets had landed harmlessly near the border with the Gaza Strip.

An Israeli air strike on Sunday was aimed at two Palestinian militants, one of whom was critically wounded, as was one of the bystanders.

Reuters and The Associated Press contributed to this report.

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