A weak central government has also allowed for the proliferation of radical Islamist cells, Karim Mezran, co-author of the Atlantic Council study, said Thursday.
Some observers have accused Ansar al-Sharia, a shadowy Islamist extremist group in Libya, of being behind Tuesday’s attack.
But according to the SITE monitoring service, the brigade denied any role in the attack, saying in a posting on its Facebook page Wednesday that the accusations against it had been made to damage its image.
Some Libyan analysts and officials tried to play down the strength of armed Islamist radicals in the country.
“These groups are completely isolated, but they are powerful by their influence, not their numbers,” said Noman Benotman, a former member of the Libyan Islamic Fighting Group who is president of Quilliam, a London-based think tank. “The question is, to what extent they are capable of changing agendas.”
In August 2011, four months after his arrival in Benghazi as the U.S. envoy to the rebel administration in Libya, Stevens was already talking about militias. In an address to the State Department, he said that despite progress in the fight against Gaddafi, there was a security “vacuum” and a situation in eastern Libya that involved “a lot of militias and a few police.”
In an interview with The Washington Post in June, Stevens remained concerned and said Libyan authorities were handling the militants in their own way. “The Libyans are well aware of the problem, and they are devising Libyan ways to deal with it.”
Doug Frantz and Tara Bahrampour in Washington and Michael Birnbaum in Cairo contributed to this report.