Iraqi soldiers backed by US-led coalition aircraft repelled an attack on Friday by the Islamic State group on a base where hundreds of US troops are training local security forces, officials said.

"The Iraqi Security Forces (ISF) supported by Coalition surveillance assets defeated the attack (on the Al-Asad air base in western Iraq), killing all eight attackers," a US military statement said.

About 300 members of the US security forces are at the base in the heart of Anbar province training Iraqi troops.

An Iraqi army colonel and a defence ministry official said the botched attack involved at least seven would-be suicide bombers using a military vehicle.

It came hours after IS fighters launched an offensive on the nearby town of Al-Baghdadi, one of the few in the Sunni province still under government control.

"IS gunmen launched an attack yesterday (Thursday) afternoon, targeting the police headquarters of Al-Baghdadi and two government buildings in the town centre," a police lieutenant colonel said.

He said the attackers were assisted by "sleeper cells" that were already inside the town, one of a handful in the western Sunni province of Anbar not under IS control.

An army colonel said police, army and anti-jihadist tribal forces had succeeded in repulsing the jihadists from most neighbourhoods of Al-Baghdadi on Friday.

However IS fighters still controlled some buildings and positions in the centre of the town, which lies on the Euphrates river, northwest of Baghdad, they said.

A separate Pentagon statement said a total of five air strikes were carried out near Al-Asad since Thursday morning by coalition aircraft.

A suicide car bomb, four IS "tactical units", a checkpoint and an earth mover were destroyed in the strikes, it said without elaborating.

There were no immediate reports of casualties among the Iraqi security forces.