The United States carried out a strike in Iraq on Tuesday in self-defense, a U.S. official told Reuters, hours after Israel struck Iranian-backed Hezbollah in Lebanon and as tensions escalated in the Middle East.

The official, who spoke on condition of anonymity, said the strike was caused by a threat to US-led coalition forces.

Police and medical sources told Reuters that explosions occurred inside a base used by the Iraqi Popular Mobilization Forces south of Baghdad, killing four of its members and wounding four others.

The Popular Mobilization Forces is an official security agency that includes several armed groups allied with Iran.

Hospital sources said the initial death toll was one, but two people who were seriously injured in the blasts later died, and another body was recovered from the blast site.

The explosions came after several missiles were fired at Iraq's Ain al-Asad air base, which houses US-led forces, late Thursday, without causing any damage or injuries, US and Iraqi sources said.