BAGHDAD (AP) — The U.S. military says Iraqi forces have retaken 40 villages from the Islamic State group near Mosul since a massive operation to drive the militants from the city began last week.

U.S. Air Force Brig. Gen. Matthew C. Isler said Friday that Iraqi troops are consolidating gains made east and south of the city earlier this week, but insisted "momentum" was still on their side.

The fight to retake Mosul, which fell to IS in a matter of days in the summer of 2014, is the largest military operation undertaken in Iraq since the 2003 U.S.-led invasion.

Isler says the U.S.-led coalition has stepped up airstrikes against the militants, and is carrying out three times as many as it did during previous campaigns to drive IS from other Iraqi cities.