Libyan forces based in the city of Misrata have carried out air strikes against Islamic State (IS) group militants in their stronghold of Sirte, a military source said on Sunday.

As many as 18 people were killed in the strikes, including senior ID members, said Jamal Zubia, foreign media spokesman for Libya's self-declared government in Tripoli. The claim could not immediately be confirmed with other officials.

A resident in Sirte told Reuters that air strikes on Sunday had targeted districts in and around the city, and that at least one civilian had been killed.

Air strikes on Sirte are reported frequently, often attributed to unidentified aircraft. Military forces in western Misrata, which back the Tripoli government, say they regularly carry out strikes.

Five years after the uprising that toppled Muammar Gaddafi Libya is deeply divided, with rival governments based in Tripoli and the east. Militants loyal to IS have taken advantage of a security vacuum to expand their presence, establishing control over the coastal city of Sirte last year.

Also on Sunday, a spokesman for military forces loyal to Libya's eastern government, Akram Bouhalika, said troops had clashed with suspected IS militants for the past two days about 120km (75 miles) south of the city of Ajdabiya, east of Sirte.

Eleven militants were killed and two soldiers wounded in the clashes, Bouhalika said.