Suspicion in last week's attack that killed the United States (US) ambassador to Libya and three other Americans has focused on members of a hardcore Islamist militia known for its sympathies to al-Qaida, its fierce animosity to the US and its intimidation of other Muslims who don't conform to its harsh ideology.
That doesn't mean Libyan authorities will move against Ansar al-Shariah soon. The group is among the most powerful of the many, heavily armed militias that the government relies on to keep security in Benghazi.
In fact, it guards one of Benghazi's main hospitals.
Libya's militias are a legacy of last year's bloody civil war that led to the ouster and killing of longtime dictator Moammar Gaddafi, and their continued power underscores the weakness of the country's new political leadership nearly a year after the war ended.
With a range of ideologies, the militias arose from local groups that took up arms and battled Gaddafi's forces. Across the country, they still resist integration into the armed forces and remain in many places the sole forces keeping a fragile sense of order.