Iraq’s official security force, the Popular Mobilization Forces (PMF), said its command post at the Qalso military base about 50 kilometers south of Baghdad was hit by a huge explosion on Friday night, which two security sources said was caused by an airstrike.

Two sources at a hospital in the nearby city of Hilla said one PMF fighter was killed and six others were wounded.

“The explosion caused material damage and casualties,” the PMF said in a statement, adding that a team was investigating.

Two security sources said it was unclear who was responsible for the strike.

A U.S. official said the United States is not conducting any military activities in Iraq.

Sources said Israel launched an attack on Iranian territory on Friday, days after Iran attacked Israel with drones and missiles.

The PMF began as a group of armed factions, many with close ties to Iran, and was later recognized by Iraqi authorities as a formal security force.

Factions within the PMF have been involved in months of rocket and drone attacks on U.S. forces in Iraq during Israel’s Gaza operation, but have stopped doing so since early February.