Baghdad: The US military says an Iraqi soldier has been killed when two US helicopters collided while landing at a base in Baghdad.

A statement says two American troops and two other Iraqis were also wounded when the UH-60 Black Hawks crashed at about 8:55 pm in a northern section of the capital.

Military spokesman Captain Charles Calio says it is not clear how severe the collision was but it did not appear to be caused by hostile fire.

The military says it is not clear how many people were on board the aircraft and an investigation is under way.