Iraqi officials said the crash site was located about 20 miles west of Kirkuk, which is about 180 miles north of Baghdad. They spoke on condition of anonymity because they were not supposed to release the information.
Maj. Derrick Cheng, a spokesman for U.S. forces in northern Iraq, said all the dead were Americans. He declined to give more details or release their names.
The deaths raised to at least 4,236 the number of U.S. service members who have died in the Iraq war since it began in March 2003, according to an Associated Press count.
The U.S. military relies heavily on helicopters and other aircraft to ferry troops, dignitaries and supplies to avoid the threat of ambushes and roadside bombs in Iraq.
At least 70 U.S. helicopters have gone down since the war started in March 2003, according to military figures. Of those, 36 were confirmed to have been shot down.
The most recent previous incident was on Nov. 15, when a helicopter that made a hard landing after hitting wires in the northern city of Mosul killed two American soldiers.
A Russian-made cargo plane chartered by FedEx also crashed in November after reporting a malfunction west of Baghdad, leaving the seven crew members dead.
The Jan. 2005 crash of a U.S. Marine CH-53 Sea Stallion helicopter in western Iraq claimed 31 lives
-- the biggest single U.S. loss of life in the Iraq war. Investigators determined the crash was not due to hostile fire.