At least three fighters were killed and six others wounded in a drone strike on an Iran-backed militia headquarters in eastern Baghdad on Thursday, police and security sources told Reuters.
Police sources and eyewitnesses said at least two rockets struck a building used by al-Nujaba'a.
A group spokesman said three of the group's fighters were killed, including a local commander in al-Nujaba'a. The spokesman accused the United States of carrying out the attack.
Iraqi police and security sources said they had no further detail on who might have carried out the strike pending a government investigation.
Last month, the United States carried out retaliatory air strikes in Iraq after a drone attack by Iran-aligned militants that left one US service member in critical condition and wounded two others.
The US military has already come under attack at least 100 times in Iraq and Syria since the Israel-Hamas war began in October, usually with a mix of rockets and one-way attack drones.