AFP - Four US soldiers were killed on Monday when two helicopters crashed in northern Iraq, American and Iraqi military officials said.
"Four coalition forces members were killed when two aircraft went down in northern Iraq at approximately 2:15 am (2315 GMT Sunday)," a US army spokesman said in an initial statement.
The cause of the incident is unknown but does not appear to be the result of "enemy action," a separate US military statement said later.
An Iraqi military official told AFP two helicopters were involved in the incident, while police said the crash occurred near Kirkuk, 255 kilometres (158 miles) north of the capital Baghdad.
The US military is currently taking a back seat to an increasingly large Iraqi force made up of 560,000 policemen and 260,000 military personnel, with the US providing military logistical and air support on request.
According to the Pentagon, 143,000 American troops are deployed in Iraq.
Under an agreement signed between Washington and Baghdad in November, the US military is slated to withdraw its combat troops from Iraq by the end of 2011 and must have them out of cities by the end of this June.
At least 4,236 US military personnel have died in Iraq since the 2003 invasion, according to an AFP tally based on the independent website www.icasualties.org, and including the deaths on Monday. Fifteen troops have died so far this year.
A US OH-58 Kiowa helicopter crashed on November 15 last year in the northern Iraqi city of Mosul, in the last such reported incident.
A month earlier three US soldiers were wounded when two UH-60 Blackhawk helicopters crashed during landing in their base in Baghdad.
The UH-60 is the workhorse of the US military and operates in pairs. Each aircraft crew usually comprises two pilots and two gunners. Blackhawks routinely throw magnesium flares to deflect any heat-seeking missiles fired at them.
The worst single crash was on November 15, 2003, when two Blackhawks collided near the main northern city of Mosul, killing 17 soldiers.
In August 2007, a Blackhawk transport chopper crashed in northern Iraq, killing 14 US military personnel.