Two Blackhawk helicopters have crashed while landing in northern Baghdad, a US military spokesman said.
One Iraqi soldier was killed and two American and two Iraqi soldiers wounded in the two crashes in the Iraqi capital's Sunni district of Adhamiyah.
Lieutenant Patrick Evans said: "Two UH-60 Blackhawks have crashed while landing at Combat Outpost Ford in Adhamiyah.
It is not known how many were on board at the time of the incident, he said.
"Enemy fire is not suspected at this time," he added.
A Reuters TV cameraman in the Sha'ab district, 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.
He said he heard an explosion after the impact, followed by the sound of shooting.
Fox News correspondent Anita McNaught, in Baghdad, said: "The Blackhawks were flying over a densely populated suburb of the capital, but the fact they crashed as they were landing on a US military base - not over houses - meant that most of the crew were able to survive."
Iraqi police said clashes had broken out between Iraqi security forces and gunmen near the crash site.
The incident came 17 days after another US military helicopter crashed in southern Iraq, killing all seven soldiers on board.
The worst single crash was in November 2003 when two Blackhawks collided near the main northern city of Mosul, killing 17 soldiers.
At the beginning of last year there was a spate of crashes, including some aircraft shot down by insurgents. http://www.military-world.net/Iraq/781.html