While the report backed up many of the administration’s longstanding claims that its response was proper, it agreed with the other reports that criticized the State Department for having inadequate security at the compound where the ambassador to Libya, J. Christopher Stevens, was killed.

“The State Department security personnel, resources and equipment were unable to counter the terrorist threat that day and required C.I.A. assistance,” it said.

The panel’s findings reflected well on the intelligence apparatus, particularly the Central Intelligence Agency. The agency “ensured sufficient security” for its facilities in Benghazi and “without a requirement to do so, ably and bravely assisted the State Department on the night of the attacks,” according to the report.

“Their actions saved lives,” the report said.

The report said the C.I.A. did not have an “intelligence failure” in the months before the attacks. In fact, the report said, the agency had increased its security because of intelligence reports showing that attacks had intensified in the area.

In the course of the investigation, the committee reviewed thousands of pages of intelligence assessments, cables, emails and other documents, and it interviewed many senior intelligence officials and people who were on the ground during the attacks — including eight security personnel who responded to them, it said.

Republican lawmakers have said that the administration, fearing political fallout from the attacks — which occurred on Sept. 11, 2012, less than two months before the presidential elections — tried to mislead the public.

In particular, the Republicans have said that Susan E. Rice, who was the ambassador to the United Nations at the time, lied on several Sunday television talk shows when she said the attacks were set off by a protest over an anti-Muslim video. They claimed that she glossed over whether the fatalities were the result of “terrorist” attacks by Al Qaeda because that would have undermined the administration’s narrative that it had all but defeated the group.