"The international community cannot accept such grave incidents," the pope said during a Sunday address at St. Peter's square.

"I hope that humanitarian corridors will be organised in a concerted way for those migrants most in need."

At least 53 migrants were killed Tuesday night in the air raid on the detention centre in the Tripoli suburb of Tajoura, held by forces loyal to the UN-recognised government.

Tripoli has blamed the strike on forces loyal to Libya commander Khalifa Haftar who controls eastern Libya and who in April launched an offensive to capture the capital.

UN agencies and humanitarian groups have repeatedly voiced concern over the plight of thousands of migrants and refugees held in detention centres near combat zones in the Libyan capital.