Libyan authorities seized back control on Saturday of the headquarters and bases of armed militias in Benghazi after armed protesters attacked them overnight in violence that killed at least 11 people and wounded more than 70.

Six members of the security forces were among those killed in the unrest that rocked Libya's second city, and were apparently "executed," a medical examiner at the Benghazi Medical Centre morgue told AFP.

"In total we've received 11 fatalities" she said, including four bodies in "civilian clothes" and another that was found at the headquarters of Raf Allah al-Sahati, an Islamist militia targeted overnight.

Violence erupted late on Friday when hundreds of protesters, some of them armed, attacked bases of paramilitary groups whose militants were former rebels who helped topple Moamer Kadhafi's regime in last year's rebellion.