A U.S. investigation released Tuesday disputed a U.N. report that found "credible evidence" that up to 90 civilians died in a raid on a western Afghan village, saying an after-battle assessment found most of the victims were Taliban fighters.

The military probe found that up to seven civilians and between 30 and 35 Taliban militants were killed in an operation in Azizabad village in the early morning hours of Aug. 22. The U.N. backed a finding by the Afghan government that all the victims were civilians.

The competing claims illustrate the difficulty of determining how many civilians fall victim in a war fought in distant mountains and densely populated villages.

U.S. officials say they face significant challenges both in identifying Taliban fighters, who mix easily with the general population, and because of incentives to falsely claim civilian casualties.

"The enemy knowingly hides behind women and children, they dress in burqas," Maj. Gen. Jeffery J. Schloesser told The Associated Press on Monday. "The enemy makes it extraordinarily difficult to avoid civilian casualties. We don''t even know it (civilian casualties occurred) until the fighting is over."

In addition, the U.S. has long said that Taliban militants pressure Afghan villagers to falsely claim civilian casualties, information warfare that does serious damage to the reputations of the U.S., NATO and the Western-backed Afghan government.