At least 44 people were killed and more than 130 wounded in an air strike on a migrant detention center in the Libyan capital Tripoli, the UN mission to the country said on Wednesday.
The Libyan National Army (LNA) denied that it had targeted the center in Tajoura, saying that armed factions allied to the Tripoli-based Government of National Accord were responsible for the attack.
It said that the factions carried out the attack after the LNA struck a military camp.
The suburb of Tajoura has several military sites belonging to pro-GNA armed groups.
United Nations Secretary-General Antonio Guterres is outraged by the raid and called for an independent investigation, his spokesman Stephane Dujarric said on Wednesday.
UN Libya envoy Ghassan Salame condemned the attack, saying in a statement that the strike “clearly amounts to the level of a war crime”.
Head of the African Union Moussa Faki Mahamat called for an independent investigation and said those responsible for the "horrific crime" should be held to account.
The UN refugee agency called for an immediate end to bringing migrants trying to cross the Mediterranean back to Libya.
Charlie Yaxley, spokesman for the UNHCR, noted that the agency had warned less than two months ago that anyone inside the Tajoura detention center was at risk of being caught in the fighting around Tripoli.
He said the UNHCR is sending medical teams to the site after the latest airstrike.
Despite chronic instability, Libya remains an important transit point for migrants fleeing conflict and instability in other parts of Africa and the Middle East.