A spokesman from the US occupation force said on Sunday at least 21 other passengers were injured when the Chinook helicopter came down.
It was the bloodiest resistance attack against occupation troops since US and British forces ousted Iraqi President Saddam Hussein on 9 April.
The chopper was fired at with an "unknown weapon" as it headed to Baghdad's international airport, said a military spokesman.
Military officials said the attack occurred south of Falluja, a flashpoint town 50 km (30 miles) west of the capital.
It was the third US helicopter known to have been brought down by Iraqi resistance fighters since US President George Bush declared an end to major combat in Iraq on 1 May.
US troops told journalists to leave the area and confiscated their film as another military medical helicopter with a red cross sign on its side landed.
More resistance attacks
In Falluja, residents said a roadside bomb had hit a convoy
of US soldiers in civilian vehicles, killing four troops. US military officials could not confirm the report.
At least one vehicle was ablaze at the scene, where crowds gathered to celebrate and shout anti-US slogans.
Falluja residents celebrate near
attacked US convoy
Television pictures showed images of people dancing near the wreckage.
In a separate incident in the capital, another US soldier was killed when a convoy he was travelling in came under bomb attack, according to a military spokesman.
The soldier was evacuated to hospital after the blast in the early hours of the day, but died a few hours later.
Clashes in Abu Ghraib
Meanwhile, troops clashed with townspeople in Abu Ghraib, on the western edge of Baghdad for the second time in three days.
Witnesses reported casualties among both the Americans and Iraqis, but there was no immediate official confirmation.
On Saturday, four civilians and a policeman were killed in clashes at Abu Ghraib's marketplace.
The clashes began when US troops tried to clear market stalls from a main road, according to witnesses.
Leaflets circulating in the capital and attributed by locals to resistance fighters have proclaimed the first two days of November "days of resistance" to mark the 6-month anniversary of President George Bush's 1 May announcement that major combat was over.