Rival factions battled across Libya's capital on Saturday in the worst fighting for two years and portending a return to violence amid a long political stalemate.
The Tripoli government's health ministry gave a preliminary death toll of 12 people, with 87 injured, but did not say how many were civilians or fighters.
Sustained fighting in the city over the control of government would likely plunge Libya back into full-blown war after two years of comparative peace that brought an abortive political process aimed at holding national elections.
A months-long standoff for power in Libya has pitted the Tripoli-based Government of National Unity (GNU) under Abdulhamid al-Dbeibah against a rival administration under Fathi Bashagha that is backed by the eastern-based parliament.
Clashes erupted overnight as one of Tripoli's main groups assaulted a base held by another, witnesses there said, leading to hours of shooting and blasts.
The fighting intensified later on Saturday morning, with small-arms fire, heavy machine guns and mortars deployed in different central areas. Columns of black smoke rose across the Tripoli skyline and shooting and blasts echoed in the air.
Intense clashes later began in Janzour, on the coast road west of Tripoli and a possible access point for some forces aligned with Bashagha, people working in the area said.
An eyewitness meanwhile said a convoy of more than 300 vehicles affiliated with Bashagha had set off from Zlitan, about 150km east of Tripoli along the coastal road.
Bashagha has been based for weeks in Misrata, near to Zlitan.
To the south of Tripoli, video circulating on social media, which Reuters could not authenticate, purported to show forces of another Bashagha-aligned commander entering the Abu Salim district. Witnesses near Abu Salim said there was heavy shooting in the area.
The GNU health ministry said several hospitals and health centers had been hit in the fighting.
The United Nations Libya mission called for an immediate halt in fighting and voiced concern at shelling in civilian districts.
The mission said it was “deeply concerned” about the fighting which involved “indiscriminate medium and heavy shelling in civilian-populated neighborhoods” in Tripoli.
The mission called for all parties in Libya to “refrain from using any form of hate speech and incitement to violence.”
The US embassy also said on Twitter that Washington "is very concerned about violent clashes in Tripoli with reports of civilian casualties and property destruction."
"We stand with the Libyan people in calling for peaceful dialogue," it added.
