The Senate Homeland Security Committee's report about the Sept. 11 attacks on the US mission and a nearby annex, which killed four Americans, including the US ambassador to Libya, faulted intelligence agencies for not having enough focus on Libyan extremists. It also faulted the State Department for waiting for specific warnings instead of acting on security.

The assessment follows a scathing report by an independent State Department accountability review board that resulted in a top security official and three others at the department stepping down.

The attack, in which US Ambassador Christopher Stevens died, has put diplomatic security practices at posts in insecure areas under scrutiny and raised questions about whether intelligence on terrorism in the region was adequate.

The Senate report said the lack of specific intelligence of an imminent threat in Benghazi "may reflect a failure" in the intelligence community's focus on terrorist groups that have weak or no operational ties to al Qaeda and its affiliates.

"With Osama bin Laden dead and core al Qaeda weakened, a new collection of violent Islamist extremist organizations and cells have emerged in the last two to three years," the report said. That trend has been seen in the "Arab Spring" countries undergoing political transition or military conflict, it said.

The report recommended that US intelligence agencies "broaden and deepen their focus in Libya and beyond, on nascent violent Islamist extremist groups in the region that lack strong operational ties to core al Qaeda or its main affiliate groups."

Neither the Senate report nor the unclassified accountability review board report pinned blame for the Benghazi attack on a specific group. The FBI is investigating who was behind the assaults.

President Barack Obama, in an interview on NBC's "Meet the Press" on Sunday, said the United States had some "very good leads" about who carried out the attacks. He did not provide any details.

The Senate committee report said the State Department should not have waited for specific warnings before acting on improving security in Benghazi.

It also said that it was widely known that the post-revolution Libyan government was "incapable of performing its duty to protect US diplomatic facilities and personnel," but the State Department failed to take adequate steps to fill the security gap.

"Despite the inability of the Libyan government to fulfill its duties to secure the facility, the increasingly dangerous threat assessments, and a particularly vulnerable facility, the Department of State officials did not conclude the facility in Benghazi should be closed or temporarily shut down," the report said. "That was a grievous mistake."

Center>Copyright Reuters, 2012