UPDATE 1-Air strike hits detention centre for migrants in suburb of Libyan capital -official

An air strike late on Tuesday hit a detention centre for migrants in the Tajoura suburb of the Libyan capital of Tripoli, an official said.

There were casualties among the migrants, said the official who works in the department to combat illegal migration that runs the centre. The U.N. refugee agency UNHCR said on Twitter that it was "extremely concerned about ... accounts of refugees and migrants deceased".

No more details were immediately available. Tajoura is home to several military camps of forces allied to Libya's internationally recognised government which has been battling eastern forces trying to take Tripoli.

On Monday, the eastern-based Libyan National Army (LNA) said it would start heavy air strikes on targets in Tripoli after "traditional means" of war had been exhausted. The LNA has failed to take Tripoli in three months of fighting and last week lost its main forward base in Gharyan which was taken back by Tripoli forces.

Libya is a main departure point for migrants from Africa and Arab countries trying to reach Italy by boat. Thousands are held in government-run detention centres.