The clashes between backers of rival governments killed at least 12 people and damaged six hospitals in the Libyan capital Tripoli, sparking fears that a political crisis could spiral into a major new conflict, Agence France-Presse (AFP) reported.
According to the earlier reports, small arms fire and explosions rocked several city districts overnight and into Saturday, and smoke was seen rising from the damaged buildings.
Early on Saturday evening, the health ministry in Tripoli gave a preliminary toll of 12 dead and 87 wounded from the fighting.
Six hospitals were hit and ambulances were unable to reach areas affected by the clashes, the ministry had said earlier, condemning "war crimes."
The two rival administrations exchanged blame as videos posted online showed burned-out cars and buildings riddled with bullet holes, as well as a mosque on fire.
The United Nations Libya mission called for "an immediate cessation of hostilities," citing "ongoing armed clashes including indiscriminate medium and heavy shelling in civilian-populated neighborhoods" that it said had damaged hospitals.
The U.S. Embassy in Libya said it was "very concerned" about the clashes.
The clashes took place in Tripoli's city center after one of the capital's strongest groups assaulted the base of a rival force, witnesses said.
"This is horrible. My family and I could not sleep because of the clashes. The sound was too loud and too frightening," said Abdulmenam Salem, a central Tripoli resident. "We stayed awake in case we had to leave quickly. It's a terrible feeling."
Major armed forces backing each side in Libya's political dispute have repeatedly mobilized around Tripoli in recent weeks, with large convoys of military vehicles moving around the city and threatening force to obtain their goals.
One man was killed in the shooting, two medical sources and a friend of his told Reuters. Pictures and videos shared online of the city center, which Reuters could not immediately verify, showed military vehicles speeding through the streets, fighters shooting and local residents trying to douse fires.
Ali, a 23-year-old student who declined to give his surname, said he fled his apartment along with his family during the night after bullets struck their building. "We could not stay any longer and survive," he added.
The main Libyan standoff pits the Government of National Unity in Tripoli under Prime Minister Abdul Hamid Mohammed Dbeibah against a rival administration under Fathi Bashagha, which is backed by the eastern-based parliament.
The U.N. mission in the country warned this week against any attempt to resolve the dispute through violence.
Bashagha tried to enter Tripoli in May, leading to an hourslong shootout that forced him to leave. He has indicated recently that he may try to enter the capital again.
This week factions backing Dbeibah paraded around Tripoli in a show of force, saying they would not allow Bashagha to enter.