Almost 40 migrants have been killed in an air strike on their detention centre in a Tripoli suburb. The attack has been blamed on Khalifa Haftar, who has been trying for three months to seize the capital.
At least 70 people were injured in the raid on Tajoura, according to an emergency services spokesman.
"This is a preliminary assessment and the toll could rise," said the same spokesman.
He said 120 migrants were detained in the hangar which was directly hit by the strike.
Bodies were strewn on the floor of the hangar, mixed with the belongings and blood-soaked clothes of migrants, a French news agency photographer said.
Rescuers were searching for survivors under the rubble, while dozens of ambulances rushed to the scene.
In a statement, the internationally recognised national unity government (GNA) based in Tripoli denounced the attack as a "heinous crime" and blamed it on the "war criminal Khalifa Haftar".
Haftar, who controls much of eastern and southern Libya, in early April launched an offensive to take the capital.
The GNA accused pro-Haftar forces of having carried out a "premeditated" and "precise" attack on the migrant centre.
The African Union has condemned the air strike and demanded that those responsible for the "horrific crime" be held to account.
In a statement, the chairman of the AU Commission Moussa Faki Mahamat called for "an independent investigation to be conducted to ensure that those responsible for this horrific crime . . . be brought to account".