Three children, all sisters, were killed, and their mother and a fourth sister wounded in an air strike that hit a house near a military intelligence camp in Libya's capital on Monday, according to a report by Reuters.
The mother was in critical condition and her daughter had emergency surgery to amputate a leg after the strike in the Al Fornaj neighbourhood of southern Tripoli, the Tripoli-based Health Ministry and hospital officials said.
Libya's internationally recognised government blamed the strike on forces of Khalifa Haftar, the commander based in the east of the North African country who has been trying to seize Tripoli in the west in a ground and air campaign since April.
A Reuters reporter saw a heavily damaged two-storey house which witnesses said had been hit around midday. The family living there were among those displaced from the outskirts of Tripoli since the start of Haftar's campaign, residents said.
One neighbour, Walid Khamis, said he had heard a single warplane before the strike. "It circled, dipped, then launched," he said.
A taxi driver whose vehicle was damaged said: "I was sleeping and when I heard the strike I woke up. They're our neighbours. Then we started to take out the children" from the rubble.
The spokesman for Haftar's forces, Ahmed Mismari, said on Monday that air strikes including one against a military intelligence camp in Al Fornaj had "caused heavy losses in lives and equipment".
About 30 metres from the house was the entrance to a compound which a security official at the site said was a military intelligence camp. The camp appeared undamaged.
The conflict in and around Tripoli has killed and wounded hundreds of civilians and more than 120,000 have been displaced, but Haftar's offensive has not breached the city's southern defences.
The UN mission to Libya said in a statement that it "condemns in the strongest possible terms the reckless disregard for the lives of innocent people and calls for the immediate cessation of such indiscriminate attacks".
It noted that the attack came just over a week after another strike blamed on Haftar's forces wounded several children at a riding club near the UN base in western Tripoli. Mismari said on Monday that an ammunition store had been targeted 200 metres from the riding club.
Haftar is backed by Egypt and the United Arab Emirates, while Turkey supports the Tripoli government.
Oil-producing Libya has been in turmoil since the autocratic rule of Muammar Gaddafi was brought to an end by a NATO-backed uprising in 2011.