WASHINGTON — Two hours after the U.S. Consulate came under attack in Benghazi, Libya, the White House was told that a militant group was claiming responsibility for the violence that killed the U.S. ambassador and three other Americans.

A State Department email sent to intelligence officials and the White House situation room said the Islamist group Ansar al-Sharia claimed responsibility on Facebook and Twitter, and also called for an attack on the U.S. Embassy in Tripoli.

The document may fuel Republican efforts to show that the White House knew it was a terrorist attack, even as the U.S. ambassador to the United Nations was saying — five days afterward — that it appeared to be a protest gone awry.

The Obama administration’s account of the Benghazi events has become a campaign issue, with Republican challenger Mitt Romney and GOP lawmakers accusing the White House of misleading Americans about the nature of the attack. But militant groups often surface after such attacks claiming responsibility and it’s difficult to immediately verify such claims.

The Associated Press and other news organizations obtained the unclassified email and two related emails from government officials who requested anonymity because they were not authorized to speak about them publicly.

The House and Senate committees that oversee intelligence received a raft of documents from the Office of Director of National Intelligence on Monday, two congressional aides said. Congressional staffers combing through the documents have found a kaleidoscope of sometimes conflicting intelligence, backing up much of what intelligence officials explained over the past several weeks.

But members of both committees are still complaining that the original briefing they were given just after the Tuesday, Sept. 11 attack, differed markedly from the explanation the CIA director David Petraeus gave them by the end of that week. In that first briefing, just 12 hours after consulate was burned down, the intelligence committees received a report that it was a military style assault, but just days later, Petraeus stressed that militants had infiltrated a mob, a U.S. official said.

U.S. intelligence officials have said Petraeus outlined that extremists were believed to be in the crowd, and carried out the attack, and also stressed the picture was still evolving.

A U.S. intelligence official said Wednesday that it was “clear from the outset that a group of people gathered that evening” but that it took until the week after the attack to determine “whether extremists took over a crowd or if the guys who showed up were all militants.” The official said the briefing included the analysis that the “attacks that appeared spontaneous,” but also mentioned possible links to regional al-Qaida groups.

Meanwhile, the Tunisian government said it has arrested a 28-year-old Tunisian linked to the U.S. Consulate attack. Interior Ministry spokesman Tarrouch Khaled said Wednesday that the suspect, Ali Harzi, was in custody in Tunis. Khaled told the AP “his case is in the hands of justice,” but did not elaborate.

Secretary of State Hillary Rodham Clinton said Wednesday that the review board she appointed to investigate the attack is “looking at everything,” rather than “cherry picking one story here or one document there.”

White House press secretary Jay Carney said the emails represented just one piece of information the administration was receiving at the time.

“There were emails about all sorts of information that was becoming available in the aftermath of the attack,” Carney said. “The whole point of an intelligence community and what they do is to assess strands of information and make judgments about what happened and who is responsible.”

Carney, traveling with President Barack Obama Wednesday on Air Force One, said the emails were unclassified and referred to assertions made on a social media site.

There were a series of three emails sent by State Department officials in Washington as events unfolded on Sept. 11. Among the recipients was the White House situation room.

The first email said that the State Department’s regional security officer reported the mission in Benghazi was under attack, and that “20 armed people fired shots.” It said that Ambassador Chris Stevens, who was killed in the attack, was in Benghazi, and that Stevens and four others were in the compound’s safe haven.

Forty-nine minutes later, an email said that the firing at the consulate “has stopped and the compound has been cleared,” while a response team was attempting to locate people.

The next message, one hour and 13 minutes after the second and some two hours after the attack began, a message reported that Ansar-al-Sharia claimed responsibility for the attack.

“Embassy Tripoli reports the group claimed responsibility on Faceboook and Twitter and has called for an attack on Embassy Tripoli,” it said.

Nearly six hours after the initial attack, a State Department memo said the shelter location for the Americans was receiving mortar fire and “there are reports of injuries.”

Ansar al-Sharia bragged to members of al-Qaida in the Islamic Maghreb that it was responsible for the attack, according to recordings of phone calls intercepted by U.S. intelligence. But the group has publicly denied having anything to do with the attack.

Clinton, speaking to reporters at the State Department, said, “You know, posting something on Facebook is not in and of itself evidence and I think it just underscores how fluid the reporting was at the time and continued some time to be.”

She added, “What I keep in mind is that four brave Americans were killed and we will find out what happened, we will take whatever measures are necessary to fix anything that needs to be fixed and we will bring those to justice who committed these murders.”

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Associated Press writers Matthew Lee and Kimberly Dozier contributed to this story.

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