The Islamic State group is using tens of thousands of people as "human shields" in and around Mosul while the Iraqi forces are waging a large-scale offensive aimed at retaking the country's second-largest city, the U.N. human rights office said Friday.

Here is a look at the main developments on the 12th day of the Mosul offensive.

NEW MOSUL HORRORS

The extremist group has massacred perceived opponents on several occasions, and is widely believed to be rooting out anyone who could potentially rise up against it, focusing on Iraqis with military training or past links to security forces.

The U.N. office said civilians from across the region south of Mosul were being herded into Hamam al-Alil, a militant-held town where the population has more than doubled to 60,000 since the forced displacement began.

There, the militants separated former members of the security forces from women and children, and took both groups onward to Mosul. They killed 190 former security forces in a military base on the southern edge of the city and killed 42 civilians at another base for refusing to join the extremists. Another 24 people were reportedly shot dead on Tuesday.

US STEPS IN

The U.S. military, which is providing airstrikes and ground support for the operation, said it tried to disrupt the forced displacement of civilians south of Mosul earlier this week by striking militant vehicles being used in the forced push.

U.S. Air Force Brig. Gen. Matthew C. Isler said the U.S.-led coalition conducted "precision strikes" on vehicles that were unoccupied and far enough away from civilians to avoid harming them.

The U.S. is providing airstrikes and ground support for the Mosul offensive. More than 100 American soldiers are embedded with Iraqi units and hundreds more are based in staging areas. An American soldier was killed by a roadside bomb last week.

CONSOLIDATING GAINS

Isler said Iraqi forces have retaken 40 villages from IS near Mosul since the operation began. But most of the fighting has taken place in a belt of sparsely-populated farming communities outside the city.

Isler said Iraqi troops were consolidating gains made east and south of the city earlier this week, but insisted "momentum" was still on their side. He 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.

Iraqi forces are within 4 miles (6 kilometers) from the edge of Mosul on the eastern front, where the elite special forces are leading the charge. But progress has been slower in the south, where Iraqi forces are still 20 miles (35 kilometers) from the city.