There has been renewed fighting between rival militias on the outskirts of the Libyan capital, Tripoli, a day after at least 43 people died in clashes.
The latest violence in the suburb of Tajoura, involving local militiamen and fighters from Misrata, left one dead.
Friday's clashes occurred after protesters marched on the headquarters of the Misrata militia to demand that it leave Tripoli, and were fired upon.
The government is struggling to contain militias who control parts of Libya.
On Saturday Prime Minister Ali Zeidan confirmed that fresh fighting had taken place in Tajoura.
He urged all sides to "exercise maximum restraint", adding: "No forces from outside Tripoli should attempt to enter the city because the situation is very tense and could escalate further."
AFP quoted Mr Zeidan as saying: "The coming hours and days will be decisive for the history of Libya and the success of the revolution."
The BBC's Rana Jawad in Tripoli says Tajoura is seen as the gateway to the capital and the latest fighting was sparked when an armed convoy from Misrata entered it in an apparent attempt to make its way to the centre.
Misrata is about 200km to the east of the capital.
Our correspondent says armed groups halted the convoy, which retreated 15km (9 miles) away, but that live rounds were exchanged for some time afterward.
US Secretary of State John Kerry said in a statement that he was "deeply concerned" by the latest clashes and urged "all sides to exercise restraint and restore calm".
Government-linked militias set up checkpoints across the capital amid tightened security for the funerals of many of those killed on Friday.
Officials have updated the death toll from Friday's violence from 31 to 43. About 500 people were wounded.
Friday's fighting began after demonstrators marched on the headquarters of the Misrata brigades in the capital's Ghargour district.
Mr Zeidan said the protest march had been "peaceful and came under fire when it entered Ghargour".
However, Libya's al-Ahrar television quoted Taher Basha Agha, the head of the Misrata militia at Ghargour, as saying that the protesters were armed.
"It was not a peaceful demonstration. They carried light arms and shot at us," he was quoted as saying.
Witnesses said the militiamen had initially fired to ward off the protesters, some of whom were children, but shot at the crowd when it continued to advance.
Other witnesses said armed men returned hours later to storm the militia HQ, with some buildings set on fire.
It is unclear how many casualties were caused at the initial protest and at the later fighting.
A militia group calling itself the Shield of Libya said on Saturday it had secured Ghargour and that the Misrata fighters had withdrawn.
The Misrata militia was involved in clashes in the capital last week which left two people dead.
There have been increasing demands from civilians that the militias - which emerged during the 2011 revolution - disband or join the army, in line with an end-of-year deadline set by the interim government in Tripoli.
Some militiamen have been given salaries and taken into the government security forces but many still remain loyal to their own commanders.
Last month, Mr Zeidan was briefly seized by a militia group in Tripoli.
Two years after the overthrow of Col Muammar Gaddafi, Libya still has no constitution and divisions between secular and Islamist forces have paralysed parliament.