US warplanes have carried out air strikes on positions of the Islamic State of Iraq and the Levant (ISIL) 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 (ISIL) organisation were carried out today, causing heavy losses... in Sirte," prime minister Fayez al-Sarraj said in a televised speech on Monday.

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

"At the request of the Libya

The Tripoli-based GNA launched an operation in May to retake the ISIL bastion of Sirte, the hometown of slain dictator Muammar Qaddafi, which the fighters have controlled since June 2015.
n 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.