Updated

A Libyan militia spokesman says fierce clashes are underway in the central city of Sirte, which is under control of Islamic State extremists.

Mohammed Shamia, a spokesman for a militia known as Brigade 166 that answers to Libya's government based in the capital, Tripoli, says fighting broke out in Sirte early on Wednesday.

Libya is divided between two rival governments and parliaments.

Shamia says the militia is advancing from Sirte's outskirts, trying to pressure the IS extremists, who have recently expanded their territorial gains in Libya.

Shamia says at least nine IS militants, including Algerian and Tunisian fighters, were killed, as well as one militiaman.

However, a statement purportedly from Libya's IS branch posted photographs on Twitter showing vehicles and weapons the extremists claim to have seized from the militia.