Two U.S. Black Hawk helicopters collided while landing at an American combat outpost in northern Baghdad on Saturday, the U.S. military said.
One Iraqi soldier was killed and two American and two Iraqi soldiers were injured, military spokesman Lieutenant Patrick Evans said in an e-mail to Reuters.
"Two UH-60 Black Hawks have crashed while landing at Combat Outpost Ford in (the northern Baghdad district of) Adhamiya about 8:55 p.m. Baghdad time (1755 GMT) this evening," he said.
"The situation is under control. Emergency services are on the scene. It is unknown how many were on board at the time of the incident. Enemy fire is not suspected at this time."
A Reuters television cameraman in the Sha'ab district of northern Baghdad, near Adhamiya, said he saw two helicopters circling overhead. The engine of one of them made a thudding sound as it lost altitude and crashed.
The cameraman said he heard an explosion after the impact, followed by the sound of shooting.
Iraqi police confirmed the crash. They gave no further details, but said clashes had broken out between Iraqi security forces and gunmen near the crash site.
But the U.S. military said the crash had taken place at its base and it was not aware of any clashes in the area.
The incident was the second major U.S. military helicopter crash in Iraq in weeks. Last month, seven U.S. soldiers were killed when a transport helicopter crashed in southern Iraq in an incident the military blamed on mechanical failure.