The Iraqi government said on Wednesday that Iraqi special forces had killed 85 insurgents in a militant training camp near the northern Iraqi city of Tikrit. The US military, which provided ground and air support, said it could not confirm the death toll.
If correct, it would be one of the biggest blows to fighters in the two-year insurgency.
The dead include Sudanese, Algerians, Moroccans and Saudis.
Only one man, an Algerian, was captured.
Around seven police commandos were also killed in the fighting.
It is unclear how all but one insurgent came to be killed and how none were wounded.
The suspected training camp was in a remote location west of Tikrit and Samarra, where US troops have had a presence for nearly two years. It is not clear how such a large camp could have been set up without being detected earlier.
The Iraqi government has simply said that the operation was a success.
In a string of other attacks nationwide on Wednesday, a girl was killed in a mortar attack on her school in Baghdad, and a teacher and two students were killed in an assault on their car south of the capital.