Chinook tragedy is US military's deadliest incident in country for more than a year.
Seven American soldiers were killed on Thursday when their transport helicopter crashed in southern Iraq, the deadliest such incident in the country in more than a year, the US military said.
The CH-47 Chinook crashed about 100 kilometres west of the main southern port city of Basra as it was flying as part of four-aircraft convoy flying from Kuwait to the northern city of Balad, it said.
"The seven soldiers were the only ones on board the Chinook at the time of the crash," the US military said in a statement.
The crash comes just two days after US General Raymond Odierno took over as the new commander of US-led forces in Iraq from General David Petraeus.
British military spokesman Major Paul Smyth said a British quick reaction force was despatched from Basra and a British road convoy in the vicinity was diverted to the scene of the crash.
He said both British and US personnel were at the scene.
The US military said the incident was under investigation. "However enemy activity is not suspected," it added.
"It is a tough day for the coalition and we are deeply saddened by the loss of our soldiers," said Colonel Bill Buckner, a spokesman for the US military.
The crash was the worst since August 2007 when a US Blackhawk transport chopper crashed in northern Iraq, killing 14 US military personnel.
Two American soldiers were wounded when their helicopter crashed south of the Iraqi capital Baghdad in June this year.
The worst single US chopper crash was on November 15, 2003, when two Blackhawks collided near the main northern city of Mosul, killing 17 soldiers.
In January and February last year there was a spate of crashes, including some shot down by an insurgent cell which deployed anti-aircraft crews north of Baghdad. US forces have since hunted down those gunners.
The latest US deaths bring to 4,168 the number of US soldiers killed in Iraq since the 2003 invasion, according to an AFP count based on independent website icasualties.org.
The military's losses have been declining in the past few months on the back of an overall fall in violence across the country.
The latest deaths bring to 17 the number of US service members killed in Iraq so far this month, compared to 66 slain in September 2007.
In August, 23 soldiers were reported killed in the country.