At least 15 people were killed and 95 hurt in Tripoli after a peaceful demonstration calling on unruly militias to leave the Libyan capital turned violent on Friday, a Libyan official said.

At least 15 people were killed and 95 hurt in Tripoli after a peaceful demonstration calling on unruly militias to leave the Libyan capital turned violent on Friday, a Libyan official said.

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

"Fifteen dead and 95 wounded, several of them seriously, have been admitted to Tripoli hospitals," a health ministry spokesman said.

He was unable to give a breakdown between those killed in the demonstration and those who died in a subsequent assault on the militia headquarters.

"It's total confusion," he said.

Violence erupted when gunmen fired at hundreds of demonstrators carrying white flags from inside villas in the southern Tripoli district of Gharghour where the Misrata militia has its headquarters.

The shooting sparked a violent response in which armed men assaulted the villas and set them on fire.

A witness, who identified himself only as Ibrahim, said "most of the members of the militia barricaded themselves inside one single villa."

He later said the militiamen had evacuated the final villa and fled, adding that some militiamen had been wounded and others arrested.

Other witnesses said heavy gunfire could be heard in Gharghour and that smoke was rising from the district.

Sadat al-Badri, president of the Tripoli local council, or town hall, who had called for the protest, told AFP the shots fired at the hundreds of demonstrators came from inside the headquarters.

"Tensions are on the rise in Tripoli. We're going to announce a general strike and launch a civil disobedience campaign until these militias leave," he said.

At the Friday's prayers held hours earlier, Imams in their sermons backed the call to protest against militias issued by the town hall as well as Libya's mufti, the highest religious authority.

Hundreds of people carrying white flags in a sign of peace, as well as the national flag, and singing the national anthem had assembled in the capital's Meliana Square.

They then marched to the Misrata militia headquarters in the Gharghour district to press their demands when gunmen inside fired into the air to scare them off.

When the crowd continued to approach the building, the gunmen started firing at them, said an AFP correspondent who saw two wounded, including one hit in the stomach.

A leader of the militia from Misrata, east of the capital, told private television channel Al-Naba that the demonstrators had opened fire first.

The march was sparked by violence on November 7 in which the Misrata militia also played a central role, illustrating again the instability of Libya.

One of the group's leaders, Nuri Friwan, had been fatally wounded in fighting at a checkpoint manned by other ex-rebels, and two people were killed in subsequent fighting.

One Western diplomat said the situation was becoming "increasingly critical," and the British, French, Italian and US embassies issued a joint statement calling for Libyans to "put aside their differences."

Residents of Tripoli frequently demonstrate against the militias, who have rejected calls from a weak central government to leave the capital.

Just weeks ago, armed men seized Prime Minister Ali Zeidan and held him for several hours before releasing him.

The head of an interior ministry anti-crime unit later boasted that he was behind the "arrest" and that he was "proud" of it.