The Islamic State terror group has claimed responsibility for the explosion that killed a U.S. soldier Tuesday in Afghanistan’s Nangarhar province. ISIS’s Amaq news agency said it had caused the soldier’s death, using an IED, which also killed three Afghan soldiers. The soldier was killed during a counterterrorism mission targeting the extremist group. An investigation has begun to look into the cause of the incident. A U.S.-led military coalition has carried out airstrikes in the area within the last week against ISIS forces.