At least five people were wounded and a stray bullet entered a hospital, causing panic and increasing concerns about Libya's precarious security situation a year after the ouster of Muammar Gaddafi.

By early afternoon the headquarters of a Supreme Security Committee (SSC) militia, a body set up last year to try to regulate armed groups, was in flames and being looted by members of a rival militia faction, witnesses said. Local shops were also looted.

The fight erupted just after midnight due to a dispute over a detained member of one of the armed groups, residents in the southern district of Sidi Khalifa said.

Both militias are affiliated to the SSC, an umbrella group for various armed groups that refused to join the official police or army, saying they were still run by Gaddafi loyalists.

Civilians blocked the street where the fighting raged to prevent cars from entering the battleground where the sound of gunfire rang out. Many civilians went home to get their own arms.

"We called the police early in the morning to help us stop the shooting, but no one came," resident Khaled Mohamed told Reuters.

A stray bullet caused panic at the nearby Tripoli Central Hospital, sending doctors and nurses running for cover. Dr. Khaled Ben Nour said five casualties had been brought in.

"We have real patients with real needs. These rogue militias need to leave us in peace so we can do our jobs," Ben Nour said.