The U.S. military said 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 ISIS 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 said 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.
Meanwhile, the U.N. human rights office said Friday ISIS appears to be using tens of thousands of people as "human shields" in and around Mosul.
It has received reports of more than 200 people being killed for refusing to comply with IS orders or previously belonging to Iraqi security forces. It said "credible reports" suggest IS has been forcing tens of thousands from their homes in districts around Mosul.
"ISIL's depraved, cowardly strategy is to attempt to use the presence of civilian hostages to render certain points, areas or military forces immune from military operations, effectively using tens of thousands of women, men and children as human shields," spokeswoman Ravina Shamdasani said in Geneva.
She said 232 people, mostly former officers, were reportedly shot Wednesday, and 24 on Tuesday.
The Associated Press reported earlier this week that IS militants were going door to door in villages south of Mosul, ordering hundreds of civilians at gunpoint on a forced march north into the city, apparently using them as human shields.
The U.N. and rights groups have expressed fear that more than 200,000 civilians could be displaced in the opening weeks of the offensive. Mosul is still home to more than a million people.
ISIS has built up elaborate defenses on the outskirts of the city, including an extensive tunnel network, and has planted large numbers of explosive booby traps to slow the troops' progress.