Libya requested first US air raids on IS, says PM Fayez Al Sarraj

He added that the operation would be of limited duration and no US ground forces would be deployed

The first air strikes by the US against the Islamic State jihadist group in Libya on Monday were staged at the unity government's request, Libyan Prime Minister Fayez Al Sarraj said in a televised speech.

"The first American air strikes on precise positions of the Daesh (IS) organisation were carried out today, causing heavy losses... in Sirte," Sarraj said.

The operation would be of "limited duration" and no US ground forces would be deployed, he added.

The TV address confirmed a statement earlier on Monday from the Pentagon that the raids were launched in response to a request from the Libyan national unity government.

The raids, the first such US military intervention co-ordinated with the Libyan unity government, aim to support pro-government forces "seeking to defeat ISIL in its primary stronghold in Libya," Pentagon Press Secretary Peter Cook said, using another name for IS.

The Tripoli-based national unity government launched an operation in May to retake the IS stronghold of Sirte, hometown of slain dictator Muammar Gaddafi which IS has controlled since June 2015.

Western powers have become increasingly concerned at IS's presence in conflict-wracked Libya, where the chaos has left the North African country vulnerable to an influx of IS fighters, many from Syria.

The fall of Sirte, 450 kilometres east of Tripoli, would be a major blow to IS, which has been weakened in Syria and Iraq according to a 23-member international coalition fighting the group.