BENGHAZI, Libya – Residents of Libya’s second-largest city warned on Saturday of a “revolution” to get rid of armed militias and Islamic extremists after protests spurred in part by the killing of the U.S. ambassador left four dead in an unprecedented eruption of public frustration.

In a sign of how weak the country’s post-Moammar Gadhafi leadership remains, authorities tried to stem popular anger, pleading that some of the militias are needed to keep the country safe since the police and army are incapable of doing so.

A mass protest Friday against militias against the compounds of several armed groups in Benghazi lasted into early Saturday, as thousands stormed the headquarters of Ansar al-Shariah, an Islamic extremist group suspected in the Sept. 11 attack on the U.S. Consulate.