Unidentified warplanes carried out air strikes on Libya'sSirte city, targeting areas controlled by Islamic State militants in the south and west, a witness said on Thursday.

The strikes were the second on Islamic State in the city this month. Neither of Libya's rival governments nor other warring factions immediately claimed responsibility.

There were no immediate official reports of any casualties.

Libya is caught up in a conflict between two rival governments and their armed factions, leaving a security vacuum that has allowed Islamic State militants to gain ground. They have secured a base in Sirte.

Western governments are pushing for a United Nations peace agreement to form a unity administration between the rival factions, fearing the turmoil is pushing Libya into becoming a failed state.