A security headquarters in the Libyan capital Tripoli was set on fire and looted following clashes between rival armed militias.
The building is said to have been hit by a rocket-propelled grenade. The army moved in only after several hours, as the shooting died down at nightfall.
Residents said fighting erupted when two militia units authorised by the Supreme Security Committee began arguing over a detained member.
Civilians apparently took up arms to protect themselves.
A hospital doctor reported at least five casualties. Gunfire at the hospital caused staff to run for cover.
Libya’s rulers have struggled to control armed groups still competing for power, a year after Muammar Gaddafi’s death.
Libya security building hit in rival militia clashes