All nine people on board a US military helicopter have been killed after it made an emergency landing in Iraq.
The Black Hawk came down near the town of Falluja, west of Baghdad, the US military said, but the cause of the forced landing is not yet known.
Falluja is a hotbed of the Iraqi insurgency and has seen several clashes between local people and US troops.
Also on Thursday, a US cargo plane was forced to return to Baghdad airport after allegedly being hit by a missile.
A US military statement confirmed the C-5 plane - with 63 people on board - had developed "excessive engine vibrations in their number four engine". Unnamed officials said it had been hit by a surface-to-air missile.
There were no injuries.
On Wednesday, a US soldier was also killed and 34 injured in a mortar attack on their base west of Baghdad.
The helicopter was on a medical evacuation mission when it came down, according to military officials speaking on condition of anonymity.
Spokesman Brigadier General Mark Kimmit said he was unable to confirm whether the aircraft was involved in an evacuation at the time, describing its mission as "routine".
"There were no survivors," he told a news conference in Baghdad.
US HELICOPTER CRASHES IN IRAQ
2 Jan - OH-58 Delta Kiowa Warrior shot down near Falluja - one soldier killed
15 Nov - Two Black Hawks crash in Mosul, at least 17 killed
7 Nov - Black Hawk shot down near Tikrit, six killed
2 Nov - Chinook shot down near Falluja, killing 16 US soldiers
25 Oct - Black Hawk crashes near Tikrit, reportedly hit by ground fire - soldier injured
"There were nine personnel aboard the aircraft. We are working under the presumption that they are all American soldiers."
Troops have secured the crash site and an investigation is under way.
Several American helicopters have been targeted in recent months by guerrillas opposed to the US-led occupation of Iraq.
A small army helicopter was shot down near Falluja on 2 January, killing one pilot and injuring another.
In November, 17 US soldiers were killed when two Black Hawks collided under fire in Mosul.
On Wednesday evening, six mortar rounds were fired at the US Logistical Base Seitz, which is based in the so-called Sunni triangle, an area traditionally loyal to former Iraqi president Saddam Hussein.
A military spokesman said the mortars hit "a living area where [troops] have their sleeping quarters" at around 1845 (1545 GMT).
Some soldiers - mainly from the Third Corps Support Command - were treated at the scene while others were evacuated.
The Pentagon has reported the deaths of 346 American service personnel in Iraq since 1 May, when President George W Bush declared major combat over.