IRBIL, Iraq: Kurdish forces backed by airstrikes from a U.S-led coalition drove ISIS militants out of nine villages in northern Iraq Friday, Kurdish authorities said. The assault began at dawn on two fronts in the northern province of Kirkuk, and by early afternoon, peshmerga forces had taken an area of over 150 square km, the security council of the autonomous Kurdistan region said in a statement.

At least 40 insurgents were killed in the offensive in the Daquq area, some 175 km north of the Iraqi capital Baghdad, the security council said. Of around 1,500 peshmerga who took part, four lost their lives, according to Kurdish fighters who took part in the battle.

Most off the peshmerga-ISIS frontline has not moved in months.

The Kurds already control much 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.

The Security Council said Friday’s operation would “further weaken ISIS’ ability to threaten the Kurdistan region,” and said the peshmerga had taken control of the strategic Dusera heights and a stretch of the main road from Kirkuk to Baghdad.

Coalition warplanes targeted dozens of ISIS positions, providing close air support to the peshmerga and destroying a suicide car bomb, the security council said.

The peshmerga have emerged as an important ally for the coalition, pushing the insurgents back in northern Iraq and effectively expanding their region in the process. That has seen them encroach on areas over which Baghdad claims jurisdiction.

Last summer, the Kurds took full control of the disputed city of Kirkuk after the Iraqi army abandoned its bases there, but western parts of the province such as Hawija remain under ISIS control.

In the last six months, the peshmerga have cleared more than 530 square km south of Kirkuk.