At least ten workers were killed and 35 wounded in an airstrike that hit a biscuit factory in Libya on Monday in what a senior UN official said was a possible war crime.
The majority of those killed in the strike in Wadi Rabea, 21 km (13 miles) from the centre of Tripoli, were apparently migrants, while two were Libyans, UN Libya envoy Ghassan Salame told the Security Council.
Pictures posted by authorities showed several wounded people in bloodstained civilian clothes lying on beds in ambulances or medical facilities.
Tripoli has been under attack since April from forces loyal to east Libya-based commander Khalifa Haftar. The offensive by his Libyan National Army (LNA) quickly stalled, and both sides have used drones and fighter jets to carry out airstrikes amid sporadic fighting.
LNA airstrikes have often hit civilian areas in Tripoli. Officials in eastern Libya contacted by Reuters on Monday said they had no information about an airstrike by their forces.
"Regardless of whether the attack deliberately targeted the factory or was an indiscriminate attack, it may constitute a war crime," Salame said.
He also accused the LNA of causing civilian casualties by increased airstrikes with unguided bombs, according to a transcript of his speech released by the UN mission in Libya.
The LNA had conducted more than 800 drone strikes, Salame said, while forces allied to the Tripoli government had carried around 240.
Salame said there had been intensified artillery fire directed at some Tripoli districts, although he did not name the LNA. He blamed a recent rise in violence on the growing use of mercenaries and private military contractors.
He did not identify these forces, but diplomats and Tripoli officials have said that hundreds of Russian mercenaries have been fighting on Haftar's side since September.
More than 200 civilians have been killed and 128,000 displaced in the conflict, Salame said.
Since 2014, Libya has been split between rival political and military groupings based in Tripoli and the east.
Haftar has received backing from the United Arab Emirates, Egypt and Russia, as well as some support from Western powers. The Tripoli government has been backed by Turkey.
Last week the United States called on the LNA to halt its offensive on Tripoli, warning against Russian interference.
Salame said Germany's attempts to hold a conference to bring an end to the conflict in Libya were continuing with another preparatory meeting planned for Wednesday. He did not give a date for the main event.