IRBIL, Iraq — Iraqi military and police forces said Monday they have uncovered a mass grave in a small town south of the Islamic State-held city of Mosul. Initial reports say 100 bodies were found, many of them decapitated.

Brig. Gen. Yahya Rasoul, the top spokesman for the Joint Military Command, said the bodies were discovered Monday in the town of Hamam al-Alil, which was recaptured by Iraqi forces over the last three days.

Rasoul told the Associated Press that the remains were skeletons and that it was difficult to tell whether they were civilians or soldiers.

“Gangs of ISIS militants continue to commit crimes against our people,” the Iraqi military said.

Fighters from the Islamic State, also known as ISIS, have held the city of Mosul and surrounded towns and villages for more than two years.

A massive offensive by combined Iraqi forces, aided by U.S. air support, began three weeks ago.

An Iraqi federal police officer, who spoke on condition of anonymity because he had not been given permission to brief reporters, said the Iraqi forces were not sure where the dead came from.

The bodies, he said, were found buried at an agricultural school outside of Hamam al-Alil.

A forensics team from Baghdad will arrive on the site Tuesday, the Iraq military said.