US launches first anti-IS air raids in Sirte

US warplanes Monday carried out air strikes on positions of the Islamic State group in the Libyan city of Sirte for the first time, the country's unity government head announced.

"The first American air strikes on precise positions of the Daesh (IS) organisation were carried out today, causing heavy losses... in Sirte," prime minister Fayez al-Sarraj said in a televised speech.

In Washington, the Pentagon said the raids were launched in response to a request from the unity government.

"At the request of the Libyan Government of National Accord, the United States military conducted precision air strikes against ISIL targets in Sirte, Libya, to support GNA-affiliated 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 GNA launched an operation in May to retake the IS bastion of Sirte, the hometown of slain dictator Moamer Kadhafi which the jihadists have controlled since June 2015.

The fall of Sirte, 450 kilometres (280 miles) east of Tripoli, would be a major blow to IS, which has also faced a series of setbacks in Syria and Iraq.

The battle for Sirte has killed around 280 pro-government fighters and wounded more than 1,500, according to medical sources at the unity forces' command centre.

A militia set up to guard the country's main oil facilities has also been advancing on IS.

The GNA was the result of a UN-brokered power-sharing agreement struck in December, but it has yet to be endorsed by Libya's elected parliament based in the country's far east.