A fighter of Libyan forces allied with the UN-backed government runs for cover during a battle with Islamic State fighters in Sirte, Libya, July 31, 2016. [Photo/Agencies]

TRIPOLI, Aug - The US launched the first airstrikes against the Islamic State (IS) targets in the Libyan city of Sirte, at the request of Libya's UN-brokered government, the prime minister said in a televised speech.

"The first airstrikes were carried out on precise positions of the IS in Sirte, causing heavy losses," Prime Minister Fayez al-Sarraj said.

He said the airstrikes would be limited to Sirte and its surroundings.

In Washington, Pentagon confirmed the operation in a statement, saying "additional US strikes will continue to target IS in Sirte in order to enable the Government of National Accord (GNA) to make a decisive, strategic advance."

"The US stands with the international community in supporting the GNA as it strives to restore stability and security to Libya," the statement said.

It said the strikes were authorized by US President Barack Obama.

Since May, Libya's UN-backed government have been striking the IS targets in Sirte, about 450 kilometers east of the capital city Tripoli.

The IS has claimed responsibility for a series of suicide attacks in Libya.