In northeastern Syria, more than 150 people have been killed after Islamic State fighters launched a coordinated assault on a prison, aiming to free men and boys held captive by a U.S.-backed Syrian Kurdish militia. The attack prompted the U.S. military to call in airstrikes from helicopter gunships. The prison remains under siege, with Kurdish fighters claiming the Islamic State is using hundreds of boys as human shields. Nearly 700 children of alleged Islamic State fighters have been held at the prison by a U.S.-backed Kurdish militia known as the Syrian Democratic Forces. Last year, a United Nations report found conditions inside the jail amounted to torture, with prisoners packed into overcrowded cells and denied sunlight, medical care and proper nutrition.