A strike targeted a military base belonging to the former paramilitary coalition Popular Mobilization Forces (PMF) in northern Iraq on Saturday, two PMF sources told AFP.
"An airstrike, likely American, hit a PMF base south of the city of Mosul," an official said. Another source confirmed the strike took place.
The PMF is an alliance of factions now integrated into the regular army.
Bases belonging to the PMF have been hit several times since the start of the war in the Middle East, with strikes hitting Tehran-backed armed groups.
Pro-Iran factions have brigades that operate within the PMF, but have a reputation for acting on their own.
They are also part of the loose alliance of the “Islamic Resistance” in Iraq that has vowed not to stay neutral in the war and has been claiming attacks against US bases in Iraq and the region.
Iraq, long a proxy battleground between the US and Iran, had said it did not want to be dragged into the conflict engulfing the Middle East, but it has not been spared.
It was drawn into the war from the outset, with strikes blamed on the United States and Israel targeting Iran-backed groups.