BAGHDAD — The U.S. military admitted Sunday that American soldiers killed innocent civilians after opening fire on a car last month on the heavily secured Baghdad airport road.

The statement — which called the man and two women killed law-abiding citizens of Iraq — reversed earlier military claims that they were suspected militants who shot at a parked American convoy.

The military blamed the shooting on a series of misunderstandings and said neither the soldiers nor civilians involved in the incident were at fault.

The June 25 shooting deaths sparked controversy after Iraqi officials identified the three people killed as bank employees, not militants. The initial military statement claiming they were suspected militants raised concerns because it suggested that tight security on the road leading to Baghdad international airport had been penetrated.

An investigation showed the soldiers fired at the civilian car when it failed to follow orders to stop as it approached the convoy, which had pulled to the side of the road because of maintenance problems.

In violence Sunday, seven Shiite pilgrims traveling to a shrine in Baghdad were shot to death in an ambush in a Sunni town south of the capital as authorities tightened security ahead of a major religious festival that is expected to draw tens of thousands of worshippers.

The gunmen were hiding on the side of the road when they opened fire, killing the seven young men near Madain, about 14 miles southeast of Baghdad, said a police officer familiar with the incident.

Tens of thousands of people are expected to converge on the Baghdad neighborhood of Kazimiyah this week to mark the death of an eighth century Shiite saint buried in the golden-domed shrine there.