Previous reports said nine soldiers had been killed.
At least seven soldiers were killed when two helicopters took enemy fire in the largest offensive of the five- month war against terrorists, the Associated Press reported.
Defense Secretary Donald Rumsfeld said enemy forces had sustained "much larger numbers of killed and wounded, and there will be many more," and that the assault would continue.
Joint Chiefs of Staff Chairman Richard Myers said several hundred al-Qaida fighters were in the mountains of eastern Afghanistan, well-fortified with "lots of weapons."
In one incident, a Chinook helicopter was shot at and crashed. Six died in the crash or an ensuing firefight on the ground, said a senior defense official.
In the second incident, the official said one U.S. soldier was killed when a helicopter was fired on, made a hard landing and then managed to take off again. An eighth U.S. soldier was killed Saturday.
An unknown number of U.S. troops also were wounded in the incidents.