The U.S.-led coalition says Iraqi forces have made significant progress as they close in on the Islamic State-held town of Tal Afar, west of Mosul.

U.S. Army Col. Ryan Dillon, a coalition spokesman, told The Associated Press on Monday that Iraqi forces have retaken some 250 sq km (95 sq. miles) from the extremist group.

The operation to retake Tal Afar was launched early Sunday, a month after Iraq declared victory against IS in Mosul, the country’s second largest city.

Tal Afar, about 150 km (93 miles) east of the Syrian border, is in one of the last pockets of IS-held territory in Iraq.