Kurdish forces drove Islamic State militants out of villages near the Iraqi city of Kirkuk and retook nearly 55 square miles of territory from the rebel group in an offensive backed by US-led coalition airstrikes, according to a statement from the Kurdistan Region Security Council (KRSC).

The assault early on Wednesday morning consolidated Kurdish control over the strategic, oil-rich city of Kirkuk in northern Iraq, bringing Kurdish fighters closer to the IS stronghold of Hawijah, about 34 miles to the west.

KRSC said that 3,500 Kurdish armed forces, known as the peshmerga, had driven IS militants further south out of four villages near Kirkuk and secured a stretch of a strategic highway. Dozens of US-led coalition warplanes aided their ground offensive.

Ten Kurdish fighters were killed and another 16 injured, according to an anonymous Kurdish security official speaking to the Associated Press. The Kurds reported that at least 40 IS fighters were killed in the offensive, although this number has not been independently verified.

The US Defense Department reported that three US-led coalition airstrikes took place on Tuesday, which it said struck an IS tactical unit and several of the group's weapons caches. Eight additional airstrikes hit strategic IS targets nearby in Hawijah on the same day, said the DOD.

This is the fourth major offensive by the peshmerga on Kirkuk, which has created a widening buffer around the city and cleared nearly 250 square miles of territory over the past six months, according to the region's security council.

Kurdish forces have been fiercely defending the city since they took control of it last summer, after the Islamic State took over wide swaths of Iraq, including Hawijah, which prompted Iraqi soldiers to flee Kirkuk. Kurdish leaders say they will never give up the ethnically mixed city, which they, as well as Turkmen and Arabs, claim as their own.

The peshmerga, who gained battlefield experience fighting former Iraqi dictator Saddam Hussein's forces, are seen by the US and Western allies as a vital deterrent against the Islamic State, which has dubiously declared a radical Islamic "caliphate" in the territory it controls.

Apart from the gains around Kirkuk, the frontline between peshmerga and IS has hardly moved for months. The militant Islamist group has not been able to take ground from the peshmerga since the US-led coalition started bombing the insurgents.

The Kurds already control most of the territory they claim as their own, and have little incentive to push further into predominantly Arab towns and villages, except where they pose a direct threat to their region.