A rocket attack in Iraq killed an American contractor and wounded several military personnel Friday, the first US casualties from a string of recent strikes, the international coalition against the IS group said.

While the coalition did not attribute blame for the incident, it threatens to escalate already-high tensions between Washington and Tehran, which backs various paramilitary groups in Iraq that the United States has accused of being behind rocket attacks on its interests. “One US civilian contractor was killed and several US service members were wounded in a rocket attack on an Iraqi military base in Kirkuk,” the US-led coalition said in a statement.