TRIPOLI (AFP) - More than 30 people were killed and hundreds wounded in the Libyan capital when a residents' revolt against militia rule degenerated into armed clashes, a health ministry official said on Saturday.

Explosions and gunfire rocked several districts of Tripoli throughout the night after Friday's violence.

"The latest toll from the health ministry's coordination cell is 32 dead and 391 wounded," said the ministry's information office chief, Amar Mohamed Amar.

The government called for a ceasefire after a demonstration calling for a militia made up of former rebel fighters to leave the capital turned into a deadly confrontation between groups of gunmen.

The militias are holdovers from the 2011 uprising that ousted dictator Moamer Kadhafi and are a powerful force in the increasingly lawless North African country.

Witnesses said "reinforcements" in pickups mounted with anti-aircraft guns arrived overnight from the port city of Misrata, scene of some of the most brutal fighting in the 2011 uprising.

The violence erupted when gunmen fired at hundreds of marchers carrying white flags from inside villas in the south Tripoli district of Gharghour where the Misrata militia has its headquarters.

The shootings sparked a violent response in which armed men assaulted the villas and set them on fire. It was unclear how many died in the demonstration or how many were killed in the assault.

Prime Minister Ali Zeidan said at first that armed demonstrators were involved in the clashes and the security forces had not intervened "so as not to complicate the situation".

But he later backtracked to say the protest march had been "peaceful and came under fire when it entered Gharghour".

Zeidan, who himself was abducted briefly by armed men in October, had warned last week of the possibility of foreign powers intervening unless chaos ends, and called on Libyans to rebel against militias.