There were conflicting accounts concerning the legitimacy of the target.
Iraqi state TV reported the building was a prison used by ISIS as a base of operations and that the strike killed "ISIS militants." Local officials with the Mosul civil defense ministry asserted the building housed opponents of ISIS, and that the majority of those killed were civilians.
It was also unclear how many were killed in the airstrike, with estimates ranging from 30 to at least 76 people.
ISIS seized control of Mosul in June, forcibly displacing more than 300,000 residents and threatening minority groups, including Iraqi Christians.