Esam Omran Al-fetori / Reuters

The U.S. consulate in Benghazi is seen in flames on Sept. 11.

WASHINGTON -- A senior intelligence official has issued a new timeline for the events surrounding the attack on the U.S. Consulate in Benghazi, Libya, indicating a series of tragic miscalculations that left CIA officers exposed at an annex near the consulate -- but no evidence of interference from Washington or of the CIA witholding aid from the State Department, as Republican critics have alleged.

According to the timeline, CIA officials in Libya sent a security team to the consulate within 25 minutes of the report of the attack, and the U.S. military sent an unarmed drone to provide intelligence information.

Four Americans, including Ambassador Christopher Stevens, information management officer Sean Smith and security personnel Tyrone Woods and Glen Doherty, were killed in the attack Sept. 11-12.

Questions have been raised about whether the consulate had adequate security and whether the State Department responded appropriately to requests for more protection.

Also, immediately after the Benghazi attack, U.S. spy agencies produced conflicting reports on who was behind them, U.S. officials have said. Most said extremists with possible al-Qaida ties were involved. But a few reports, which the Obama administration emphasized in public statements, said the attacks could have been spontaneous protests against an anti-Muslim video made in the U.S.

According to the senior intelligence official:

• The officers on the ground in Benghazi responded quickly to the attack, risking their lives in an attempt to rescue those at the consulate.
• There was no second-guessing of decisions made on the ground and no order to anybody to stand down in providing support. "At every level in the chain of command, from the senior officers in Libya to the most senior officials in Washington, everyone was fully engaged in trying to provide whatever help they could," the official said. 
• The U.S. military provided essential support, including sending an unarmed drone and medical evacuation.
• Two U.S. security teams were involved -- one that was sent from the annex to the consulate and a tactical support team that was sent from Tripoli, each composed of approximately half a dozen security officers. Two U.S. military officers were on the team from Tripoli.

The chain of events described in the timeline:

-- Around 9:40 p.m. local time, the first call comes in to the annex that the consulate is under attack.

-- Fewer than 25 minutes later, a security team of about half a dozen leaves the annex for the consulate.

-- Over the next 25 minutes, team members approach the compound, attempt to secure heavy weapons from Libyan allies and make their way into the compound under fire.

-- At 11:11 p.m., an unarmed drone that had been requested from the U.S. military arrives over the compound.

-- By 11:30 p.m., all U.S. personnel, except for the missing ambassador, depart the compound in vehicles under fire.

-- Over the next roughly 90 minutes, the annex receives sporadic small-arms fire and rounds from rocket-propelled grenades; the security team returns fire, and the attackers disperse about 1 a.m.

-- At about the same time, the second team of security personnel lands at the Benghazi airport and tries to negotiate for transport into town. Upon learning Stevens was missing and that the situation at the annex had calmed, their focus becomes locating him, perhaps at a local hospital.

-- Still before dawn, the team at the airport secures transportation and armed escort and -- having learned that the ambassador was almost certainly dead -- heads to the annex to assist with the evacuation.

-- The second team arrives with Libyan support at the annex at 5:15 a.m., just before the mortar rounds begin to hit the annex. The two security officers were killed when they took direct mortar fire as they engaged the enemy. That attack lasted only 11 minutes then also dissipated.

-- Less than an hour later, a heavily armed Libyan military unit arrived to help evacuate all U.S. personnel.

Earlier Thursday, State Department spokesman Patrick Ventrell said a review board has been set up to examine the Benghazi attack and the government's response before and after the assault.

Catherine Chomiak is an NBC News producer. Andrea Mitchell is NBC News' senior foreign affairs correspondent.

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EPA, file

Protesters flee after security forces fired tear gas towards them outside the U.S. Embassy in Tunis, Tunisia, on Sept. 14.

Updated at 8:19 a.m. ET: TUNIS, Tunisia - A leader of radical Islamist group Ansar al-Sharia was sentenced to one year in prison on Wednesday for inciting an attack on the U.S. Embassy in Tunis last month in which four people were killed.

The conviction of Abu Ayub was the first in connection with the attack - launched to protest against an anti-Islamic film made in California. The United States has been urging authorities to jail those responsible.

"The judge decided to jail him on charges of inciting violence ... This decision is unfair ... we will go to appeal," said Rafik Ghak, a lawyer for Abu Ayub.

The authorities arrested 144 people, including two prominent leaders of Ansar al-Sharia after the embassy attack. Saif-Allah Benahssine, the leader of the group, has urged the government to release them.

Benahssine on Tuesday accused the country's government of being a puppet of the United States and un-Islamic.

Slideshow: Anger over film spreads throughout Muslim world

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Protests ignited by a controversial film that ridicules Islam's Prophet Muhammad spread throughout Muslim world.

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The United States this month requested Tunisia bring the embassy attackers to trial, pledging to continue its support for the democratic transition in Tunisia.

Tunisia expects Washington to guarantee around a fifth of its $2.2-2.5 billion borrowing needs next year to help its economy recover from last year's revolution, the country's minister of international cooperation, Riadh Betaib, told Reuters last month.

'Easy to make and use': Tunisian magazine teaches kids how to make Molotov cocktails

Meanwhile, the Tunisian government confirmed Wednesday that it has arrested a 28-year-old Tunisian reportedly linked to the U.S. Consulate attack in Libya.

Tunisian Interior Ministry spokesman Tarrouch Khaled said that Ali Harzi was in custody in Tunis. Khaled told the The Associated Press "his case is in the hands of justice." He did not elaborate.

However, Harzi's lawyer told NBC News that his client was innocent. Oulad Ali Anwar said Harzi was working in Benghazi as a house painter at the time of the attack and said he denied both attending the demonstration at the U.S. Consulate and belonging to any extremist group.

Rights group blasts 'repressive' crackdown in Tunisia, birthplace of the Arab Spring

In Washington, the State Department had no comment. Earlier this month, Defense Secretary Leon Panetta said the U.S. has been looking into the arrests of two Tunisian men being detained in Turkey reportedly in connection with attacks on a consulate in Libya last month.

Ambassador J. Christopher Stevens and three other Americans died in the attack on the U.S. diplomatic post in the Libyan city of Benghazi on Sept. 11.

NBC News' Charlene Gubash, Reuters and The Associated Press contributed to this report.

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Correction: An earlier version of this post had an incorrect date for the cable sent to the State Department by U.S. Embassy personnel in Libya.

House Republicans stepped up criticism of President Barack Obama on Friday over the deadly Sept. 11 attack on the U.S mission in Benghazi, Libya, releasing 166 pages of unclassified documents and photos that they said show administration officials repeatedly rejected “requests for increased security despite escalating violence … (and) systematically decreased existing security to dangerous and ineffective levels.”

The release of the documents, which came just days before Obama and Republican Mitt Romney discuss U.S. foreign policy in their last debate before the Nov. 6 presidential election, added to the political furor over the administration’s actions preceding the late-night attack on the U.S. consulate in Benghazi, which claimed the life of U.S. Ambassador Chris Stevens and three other Americans.

Many of the documents released by House Oversight and Government Reform Committee Chairman Darrell Issa and National Security Subcommittee Chairman Jason Chaffetz had previously been made public, but others provided new evidence of growing concern about the security situation in Benghazi, and Libya in general.

One, a June 25 memo from Stevens, referred to incidents in Benghazi in which local elements attacked foreigners and specifically mentioned signs of growing al-Qaida sympathies in the city.

 “(A) national security official shared his private opinion that the attacks were the work of extremists who are opposed to western influence in Libya,” Stevens wrote. “A number of local contacts agreed, noting that Islamic extremism appears to be on the rise in eastern Libya and the al-Qaida flag has been spotted several times flying over government buildings and training facilities in Derna (a city east of Benghazi). Other contacts disagree however suggesting that the attacks could be the work of pro-Gadhafi loyalists or individuals who have been politically and financially marginalized by the (Transitional National Council)."

Another document, a cable dated Aug. 2 and sent to the State Department by U.S. Embassy personnel in Tripoli, indicated that staff had growing concerns over security provided by Libyan militias.

“Host nation security support is lacking and cannot be depended on to provide a safe and secure environment for the diplomatic mission,” it said in part.

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In a letter to Obama, Issa, R-Calif., and Chaffetz, R-Utah, demanded the president fully answer questions about the administration’s response to the concerns.

"The American people deserve nothing less than a full explanation from this administration about these events, including why the repeated warnings about a worsening security situation appear to have been ignored by this administration,” it said. “Americans also deserve a complete explanation about your administration's decision to accelerate a normalized presence in Libya at what now appears to be at the cost of endangering American lives.”

The senior Democrat on the committee, Rep. Elijah E. Cummings, D-Md., issued a statement in which he accused Issa and Chaffetz of attempting to use the tragedy to score political points.

Issa's letter "completely ignores sworn testimony provided to the committee, recklessly omits contradictory information from the very same documents it quotes, irresponsibly promotes inaccurate information, and makes numerous allegations with no evidence to substantiate them," he wrote.

Ben Curtis / AP file

U.S. Ambassador Chris Stevens and three other Americans died in the attack on the U.S. consulate Benghazi, LIbya.

Separately, a senior U.S. intelligence official, who spoke with NBC News on condition of anonymity, said Friday that investigators still have not uncovered any evidence that the attack was preplanned.

"No one is ruling out the idea that some of the attackers may have aspired to attack the U.S. in Benghazi," the official said. "However, right now, there isn't any intelligence that the attackers preplanned their assault days or weeks in advance.  The bulk of available information supports the early assessment that the attackers launched their assault  opportunistically after they learned about the violence at the U.S. Embassy in Cairo. Of course, other factors may also have motivated participation in the attack." 

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State Department spokesman Mark Toner also cautioned that investigators are still piecing together events that led to the attack.

"An independent board is conducting a thorough review of the assault on our post in Benghazi,” he said. “Once we have the board's comprehensive account of what happened, findings and recommendations, we can fully address these matters."

The release of the documents came after the top Republican and Democrat on the Senate Intelligence Committee said they would continue to press the administration to explain why U.S. spy agencies and government spokesmen initially played down suspected al-Qaida links to the consulate attack.

More to Benghazi attacks than surface at debate

Immediately after the Benghazi attack, U.S. spy agencies produced conflicting reports on who was behind them, U.S. officials said. Most said extremists with possible al-Qaida ties were involved. But a few reports, which the Obama administration emphasized in public statements, said the attacks could have been spontaneous protests against a U.S.-made anti-Muslim video.

Ultimately, the office of the Director of National Intelligence, the top U.S. intelligence authority, declared that the events were a "deliberate and organized terrorist attack" carried out by "extremists" affiliated with or sympathetic to al-Qaida.

On Thursday, Sen. Dianne Feinstein, D-Calif., said both intelligence and security problems may have played a role in the attack.

"There's no question but that it was a terrorist attack, there is no question but that the security was inadequate and I think that there is no question that we need to work on our intelligence," Feinstein told KCBS-TV.

Clinton refuses to assign blame for Benghazi attacks 

When asked why the U.S. government initially played down the role of Islamic militants, she said: "I think what happened was the director of intelligence, who is a very good individual, put out some speaking points on the initial intelligence assessment. I think that was possibly a mistake."

But the committee's Republican vice chairman, Sen. Saxby Chambliss of Georgia, questioned whether administration officials deliberately omitted possible references to al-Qaida involvement in talking points about the Benghazi attacks.

"Talking points distributed by the administration are nearly identical to intelligence assessments within hours of the attack, except in one important way: the intelligence judgment that the attackers had ties to al-Qaida was excluded from the public points," Chambliss said in a statement on Friday.

"The administration omitted the known links to al-Qaida at almost every opportunity ... Whether this was an intentional effort by the administration to downplay the role of terrorist groups, especially al-Qaida, is one of the many issues the Senate Intelligence Committee must examine," he said.

NBC News Chief Foreign Affairs Correspondent Andrea Mitchell and NBC News producers Catherine Chomiak, Rich Gardella and Libby Leist and Reuters news service contributed to this report. 

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New evidence implicates Libyan militia in the apparent execution of dozens of detainees in the immediate wake of Moammar Gadhafi’s capture and death last year, according to Human Rights Watch.

In a 50-page report issued Wednesday, the New York-based organization said at least 66 members of Gadhafi’s convoy were captured and ‘summarily executed’ by militia based in Misrata.

By comparing mobile phone video taken by the opposition militia members with hospital morgue photographs, HRW have identified numerous detainees who were captured in Sirte and later executed at the town’s Mahari Hotel.

Slideshow: Conflict in Libya

Goran Tomasevic / REUTERS

An uprising in Libya ousts dictator Moammar Gadhafi.

Launch slideshow

“When we arrived, there were 53 bodies lying in the garden of the hotel. The first indication we had this was an execution site was that many victims had their hands tied behind their backs,“ said Peter Bouckaert, emergencies director at HRW. Volunteer workers at the scene said that relatives of additional victims had recovered their bodies prior to the Human Rights Watch visit.

"In case after case we investigated, the individuals had been videotaped alive by the opposition fighters who held them, and then found dead hours later," Bouckaert said.

HRW said these killings constitute the largest documented execution of detainees by anti-Gadhafi forces during the eight-month conflict in Libya.

One case cited by HRW is that of Ahmed Ali Yusuf al-Ghariyani, 29, a Navy recruit originally from Tawergha, a Gadhafi stronghold. In a phone video that is believed to show him in captivity, militia forces are seen to abuse and taunt him.

Al-Ghariyani’s body was later found at the Mahari Hotel and was photographed by hospital staff and buried as unidentified body number 86. He was later identified by family members from the hospital photographs.

The report also casts doubt on what HRW said is the Libyan authorities’ account of the fate of Gadhafi and his son Motassim, both of whom are officially reported to have died in cross-fire.

In video released with the report, Moammar is seen alive and bloodied in the hands of the rebels, in images similar to those widely circulated in the days after his death. 

According to the report, Motassim Gaddafi was also captured alive at the scene of the Sirte battle. He was wounded and then filmed being transported by members of a Misrata-based opposition militia to their home city. He was again filmed in a room, smoking cigarettes and drinking water. By the evening, his dead body, with a new wound on his throat that was not visible in the prior video footage, was being publicly displayed in Misrata.

Peter Brouckaert said the Libyan authorities’ refusal to accept or investigate atrocities by former rebels shows ‘a government in denial.’

“They are not in a position to confront the militia,” he said, ”It shows who’s in power in Libya.”

Calls for militias to be brought under the control of the defense or interior ministries have met resistance from some fighters.

Meanwhile, some groups have been implicated in revenge attacks and communal strife, while members of one Islamist militia have been accused of taking part in the attack on the U.S. Consulate in the eastern city Benghazi on Sept. 11 that killed four Americans, including U.S. Ambassador to Libya Chris Stevens.

In the aftermath of Stevens' death, popular resentment surged and thousands took to the streets of Benghazi demanding the dismantlement of the militias. The government has taken over some militia headquarters and appointed military officers to run the groups, and designated some "outlawed" and others "tolerated."

The Associated Press contributed to this report.

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Andina via AFP / Getty Images

Secretary of State Hillary Clinton, walking with her Peruvian counterpart Rafael Roncagliolo, traveled to Peru to promote entrepreneurship among women. During the trip, she spoke to reporters about the Benghazi attacks.

Secretary of State Hillary Clinton said Monday in an interview with NBC News that she worked day and night following the fatal attacks on the Benghazi consulate to ensure the safety of other government workers abroad.

She also discouraged the current debate about who should be blamed for the security breach that led to the attacks.

"I really believe that tragedies like what happened in Benghazi should be viewed in a non-political way," Clinton continued. "Everybody should pull together as Americans."

Rather than focusing on who to blame for the attacks, the State Department stayed "focused not on why something happened that was for the intelligence community to determine, but what was happening and could happen,” Clinton said. “We did everything we could to keep our people safe, which is my primary responsibility.”

She told CNN: "I take responsibility. I'm in charge of the State Department's 60,000-plus people all over the world, 275 posts."

The attacks on the Benghazi consulate on Sept. 11 have become a political piñata leading up to the presidential elections in November.

Republicans have blamed the Obama administration for wavering on what triggered the attack. Initially, the White House said the attacks were a spontaneous, angry response to a low-budget movie maligning the Prophet Mohammad. The Obama administration has since said the attacks were carefully planned by terrorists.

Four Americans died in the attack, including Ambassador Chris Stevens. Protests – some violent, others peaceful – emerged throughout the region and reached as far as Australia.

On Monday, when asked if the initial reports indicated that there had been an intelligence failure, Clinton said she didn’t want to engage in a “blame game.”

"What we want to do is get to the bottom of what happened, figure out what we're going to do to protect people and prevent it from happening again, and then track down who ever did it and bring them to justice," Clinton said, echoing Biden's comments during the debate.

In the media, what happened in Benghazi has become the foreign policy go-to question. Moderator Martha Raddatz made Libya the first topic of discussion during the vice presidential debate last week.

“When you take a look at what has happened just in the last few weeks, they sent the U.N. ambassador out to say that this was because of a protest and a YouTube video,” Congressman Paul Ryan said during the debate with Vice President Joe Biden. “It took the president two weeks to acknowledge that this was a terrorist attack.”

On Friday, Clinton reaffirmed U.S. support of Libya, saying pulling back would be a "costly strategic mistake."

The terrorists who attacked the mission do not represent the Libyan people, she said, noting the protests that broke out after the attacks against the militias in Libya.

Related: Clinton reaffirms support for Libya and emerging democracies

"The United States will not retreat," Clinton said on Friday. "We will keep leading and we will stay engaged in the Maghreb and everywhere in the world, including in those hard places where America’s interests and values are at stake."

NBC News' Isolde Raftery contributed to this report.

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Yuri Gripas / REUTERS

U.S. Secretary of State Hillary Clinton delivers a keynote address on "U.S. Strategic Engagement with North Africa in an Era of Change" at the Center for Strategic & International Studies in Washington on Friday.

A month after the terrorist attack on the U.S. mission in Benghazi, Libya, that killed four Americans, including Ambassador Chris Stevens, Secretary of State Hillary Clinton reaffirmed the United States' support for the new governments emerging from the Arab Spring.

Speaking at the Center for Strategic and International Studies on Friday, Clinton said the attack in Benghazi and the burning of the American School in Tunis have led some to question the promise and hope of the Arab Spring. She said she has always been clear-eyed about the challenges that were ahead.  

"Let me start by stating the obvious: Nobody should have ever thought this would be an easy road. I certainly didn't," Clinton said. 

Romney: Biden 'doubling down on denial' in explanation of Libya response

She went on to say that the United States "will not pull back our support for emerging democracies when the going gets rough. That would be a costly strategic mistake that would, I believe, undermine both our interests and our values."   

Clinton described what occurred on Sept. 11 in Benghazi as a “terrorist attack” and said she appointed a review board to examine the security procedures in Benghazi. The U.S. government is "sparing no effort" to track down the terrorists responsible for the attack, Clinton said.

The terrorists who attacked the mission do not represent the Libyan people, she added, citing the protests against the militias there.

"The United States will not retreat," Clinton said. "We will keep leading and we will stay engaged in the Maghreb and everywhere in the world, including in those hard places where America’s interests and values are at stake."

The United States is "stepping up" its counterterrorism efforts in northern Mali, Clinton said, where al-Qaida in the Islamic Maghreb is trying to expand its reach. 

"For some time, al-Qaida in the Islamic Maghreb and other terrorist groups have launched attacks and kidnappings from northern Mali into neighboring countries. Now, with the chaos and ethnic conflict there allowing these groups to carve out a larger safe haven, they are seeking to extend their reach and their networks in multiple directions," she said.

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EPA file

U.S. Ambassador to Libya Christopher Stevens, who was killed in an attack on the U.S. consulate in Benghazi, during an event in Tripoli, Libya, Sept. 12.

Documents including the full itinerary of Ambassador Christopher Stevens’s trip to Benghazi, Libya and the personnel records of Libyans employed to secure the U.S. official's mission were left behind at the U.S. consulate in Benghazi, The Washington Post reported exclusively. 

A reporter who visited the looted compound Wednesday found the sensitive documents strewn across the floor, The Post said. The State Department did not ask The Post to withhold the documents from publication.

The discovery comes almost four weeks after an attack on the U.S. consulate took the lives of Stevens, as well as information management officer Sean Smith and security personnel Tyrone Woods and Glen Doherty.

According to The Post, many other documents have likely disappeared from the compound, which is now guarded by two private security guards paid for by the compound’s Libyan owner.

FBI agents keep out of Benghazi

“Securing the site has obviously been a challenge,” Mark Toner, deputy spokesman at the State Department, told The Post when asked about conditions at the Benghazi consulate. “We had to evacuate all U.S. government personnel the night of the attack.  After the attack, we requested help securing the site, and we continue to work with the Libyan government on this front.”

One of the documents found by The Post shows Stevens and his staff were discussing the possibility of an attack in early September, two days before the assault took place. According to The Post, the memo was detailing plans for a “quick reaction force,” or QRF, to ensure the security of the mission.

“In the event of an attack on the U.S. Mission,” the document states, “QRF will request additional support from the 17th February Martyrs Brigade.”

Security on the compound appears to have been bare-bones, The Post suggests, pointing to a statement in the memo requiring guards “to acquire and maintain their own weapons and ammunition." The memo also suggests the Americans were not confident the protection from the guards would be sufficient in case of an emergency, The Post said.

Libyan president to NBC: Anti-Islam film had 'nothing to do with' US Consulate attack

Several copies of Stevens' Benghazi trip itinerary were scattered across the floor, the newspaper reported. The document included all of the envoy's planned movements during a visit that was supposed to last from Sept. 10 until Sept. 15.

Secretary of State Hillary Clinton on Wednesday vowed to pursue a full accounting of the deadly attack on the U.S. consulate in Benghazi "wherever that leads," but cautioned that it could take time for a complete picture to emerge.

"There are continuing questions about what exactly happened in Benghazi on that night three weeks ago. And we will not rest until we answer those questions and until we track down the terrorists who killed our people," Clinton said in an appearance with Kazakhstan's visiting foreign minister.

Ambassador Rice: Benghazi attack began spontaneously

"The men and women who serve this country as diplomats deserve no less than a full and accurate accounting, wherever that leads, and I am committed to seeking that for them and for those who made the ultimate sacrifice in service to our nation."

Clinton's comments followed a demand by two Republican lawmakers this week for more information about the September 11 attack, which they said occurred after Washington repeatedly turned down requests from Americans in Libya for more security at the Benghazi consulate.

U.S. Representatives Darrell Issa and Jason Chaffetz also said that the House of Representatives Oversight and Government Reform Committee will hold an Oct. 10 hearing on the security situation leading up to the Benghazi attack.

White House: Libya consulate siege that killed four was 'terrorist attack'

Reuters reported on Tuesday that the U.S. government received about a dozen intelligence reports within hours of the attack suggesting involvement by organized militant groups. Despite that, the Obama administration for nearly two weeks emphasized the role of the anti-Muslim video.

Clinton noted that the State Department had named an "accountability review board" to investigate attack, and that she had urged the group "to move as quickly as possible without sacrificing accuracy."

"I am aware too that many people are eager for answers. So am I ... and no one wants the answers more than we do here at the department," Clinton said.

"Over the course of this review, there will naturally be a number of statements made, some of which will be borne out and some of which will not. So let's establish all the facts before we jump to any conclusions and let's do so that we can get to the bottom of what did happen," she said.

Reuters contributed to this report.

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Militant groups in North Africa have benefited from lapses in security across the region as countries transition to more democratic government – increasingly funding themselves through kidnapping, a senior U.S. Treasury official said.

The U.S. estimates militant organizations received $120 million in ransoms over the past decade, including to al-Qaida in the Islamic Maghreb in recent years, said David Cohen, undersecretary for terrorism and financial intelligence.

Kidnapping for ransom was an "urgent threat," particularly in the Sahel, a belt of land spanning nearly a dozen of the world's poorest nations on the Sahara's southern rim, Cohen told reporters in Berlin on Tuesday.

"It is what has become perhaps the most challenging and fastest growing technique that terrorist organizations, in particular the affiliates of al-Qaida in North Africa and in Yemen, have been using to fund themselves over the last couple of years."

The Obama administration has been concerned about the growing power and influence of al-Qaida offshoots in Yemen, Somalia, Iraq and North Africa.

Small teams of special operations forces arrived at American embassies throughout North Africa in the months before militants launched the fiery attack on Sept. 11 that killed the U.S. ambassador in Libya. The soldiers' mission: Set up a network that could quickly strike a terrorist target or rescue a hostage.

The teams had yet to do much counterterrorism work in Libya, although the White House signed off a year ago on the plan to build the new military task force in the region and the advance teams had been there for six months, three U.S. counterterror officials and a former intelligence official told The Associated Press. All spoke only on condition of anonymity because they were not authorized to discuss the strategy publicly.

Officials say the military organization was too new to respond to the attack in Benghazi, where the administration now believes armed al-Qaida-linked militants surrounded the lightly guarded U.S. compound, set it on fire and killed Ambassador Chris Stevens and three other Americans.

Al-Qaida in North Africa emerged out of Algeria's civil conflict and has expanded south into the Sahara, raising its profile in recent years with hit-and-run attacks and kidnappings of westerners.

While the U.S. government has a policy of not paying ransoms, some European governments do so. The average ransom had gone up consistently over the years and was in the range of $5 million per payment, Cohen said.

Back in Washington, D.C., Republicans have questioned whether the Obama administration has been hiding key information or hasn't known what happened in the immediate aftermath of the attack.

On Tuesday, leaders of a congressional committee said requests for added security at the consulate in Benghazi were repeatedly denied, despite a string of less deadly terror attacks on the consulate in recent months. Those included an explosion that blew a hole in the security perimeter and another incident in which an explosive device was tossed over the consulate fence.

Secretary of State Hillary Rodham Clinton told Congress in a letter responding to the accusations that she has set up a group to investigate the Benghazi attack, and it is to begin work this week.

The Associated Press and Reuters contributed to this report.

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