Libyan forces backed by US air strikes said on Tuesday that they had taken control of one of the last districts in central Sirte occupied by Islamic State fighters.

Forces aligned with Libya's UN-backed government in Tripoli are three months into a campaign to oust Islamic State from their former North African stronghold and have captured most of the coastal city.

Since Aug. 1 their progress has been aided by US air strikes that have targeted Islamic State vehicles, weapons and fighting positions. US Africa Command said it had carried out a total of 48 strikes as of Wednesday.

The Libyan forces are mainly composed of brigades from the western city of Misrata. After they secured key sites south of central Sirte last week, fighting moved into neighbourhood Number 2, which the brigades said they had now captured.

‘On Tuesday morning clashes erupted ... that led successfully to the recapture of neighbourhood Number 2 with the cooperation of a tank unit to confront Islamic State snipers,’ said Rida Issa, a spokesman.

‘The neighbourhood is now completely under control of our forces.’

Some casualties from the fighting were arriving at Misrata's central hospital, but it was not yet clear how many had been killed and wounded said, Akram Gliwan a hospital spokesman.

Islamic State took control of Sirte last year, turning it into a base for Libyan and foreign fighters and extending their control over about 250 km (155 miles) of Libya's Mediterranean coastline.

But it has struggled to win broad support or retain territory in Libya, and losing Sirte will be a major setback for the jihadist group, already under pressure from US-backed campaigns in Iraq and Syria.