Former CIA chief Gen David Petraeus has told lawmakers that the deadly assault on a US consulate in Libya was a terror attack.
During two appearances on Capitol Hill on Friday he said the public explanation had been edited to prevent alerting groups under suspicion.
He gave evidence to the House Intelligence Committee and its Senate counterpart, both in closed session.
The testimony on Benghazi came one week after Gen Petraeus quit over an affair.
Gen Petraeus has said he left his post at the CIA only because of his extramarital affair with biographer Paula Broadwell, and not because of the CIA’s handling of the attack.
He was briefly questioned over his personal life at the start of the morning’s proceedings, but lawmakers accepted his word that his affair had not compromised national security.
Republicans have criticised the White House over the events in Benghazi, saying the administration misled the public.
US Ambassador to Libya Christopher Stevens was among the four Americans who died in Benghazi on 11 September.
Although the hearings were held behind closed doors, committee members did emerge to give reporters some insight on what happened.
Gen Petraeus told the committee the CIA was aware the attack was planned by terrorists from an early stage, New York Congressman Peter King said after the first session.
But Mr King said the general’s evidence on Friday conflicted with what he said at a hearing on 14 September.
Mr King said he had a “very different recollection” of the earlier hearing, at which lawmakers had been told the attack grew out of spontaneous protests over an anti-Islamic film.
He added that despite Gen Petraeus’ testimony on Friday it was still not clear who approved the message that the attack was linked to the protests.
Gen Petraeus told the lawmakers that references to terror groups were removed from the final version of the administration’s “talking points” on Benghazi, although he was not sure which federal agency deleted it.
Democrats said the former CIA director made clear the change was made for intelligence, not political reasons.
“The general was adamant there was no politicisation of the process, no White House interference or political agenda,” said Representative Adam Schiff. “He completely debunked that idea.”
The retired four-star general, one of the most prominent US military figures of the post-9/11 years, travelled to Libya in September to investigate what happened in Benghazi.
Congressional officials familiar with the briefings told the Associated Press that Gen Petraeus testified that security at the consulate was so lax that the attackers walked in and set fire to the facility.
Security at the CIA annex was much better, the AP reported, but the attackers had arms and broke in.
Who’s who in Petraeus affair?
- David Petraeus: A retired four-star general and the most prominent US military figure of the post-9/11 years. Formerly the top commander in Iraq and Afghanistan, Gen Petraeus retired from the military in 2011 to take the top job at the CIA
- Paula Broadwell: (Above left) A married mother-of-two who co-wrote a biography of Gen Petraeus that was published early this year. The former military intelligence analyst and graduate of West Point was granted exceptional access to the general during his tenure in Afghanistan
- Jill Kelley: (Above right) A married Florida socialite with links to the MacDill Air Force Base near Tampa who reported harassing emails to the FBI, leading to discovery of Gen Petraeus’ affair
- John Allen: Top US commander in Afghanistan, the Marine general was found to have exchanged extensive communication with Mrs Kelley. He denies any wrongdoing
- A week in scandal
- Full who’s who
Republicans were also critical of the Obama administration’s handling of security situation.
Florida Senator Marco Rubio said Gen Petraeus testimony showed that “clearly the security measures were inadequate despite an overwhelming and growing amount of information that showed the area in Benghazi was dangerous, particularly on the night of 11 September 11.”
On Thursday, the CIA launched an investigation into the conduct of its former chief.
His former mistress Paula Broadwell, 40, was found to have classified information, but both she and Gen Petraeus deny it came from him.
A CIA spokesman said the inquiry by the agency’s inspector general would see if there were any lessons to be learned from his conduct.
The CIA said in a statement on Thursday: “At the CIA we are constantly reviewing our performance. If there are lessons to be learned from this case we’ll use them to improve.
“But we’re not getting ahead of ourselves; an investigation is exploratory and doesn’t presuppose any particular outcome.”
A wider inquiry has also ensnared the US and Nato commander in Afghanistan, General John Allen.
He is under investigation for sending what officials describe as “flirtatious” emails to the Tampa hostess, Jill Kelley.