Troops found more bodies on Thursday at the scene of the clash, one of the deadliest since the fall of the Taliban in 2001.

The dead were a "mix of Taliban and anti-coalition militants" and officials were still trying to determine whether foreigners were among them, US spokesman Colonel James Yonts said.

"These were well-trained, well-armed people ... not just a rogue group. They didn't flee, they stood and fought," Yonts added.

The military previously said about 20 died in the battle on Tuesday in the remote Dehchopan district of Zabul province, about 330km southwest of the capital, Kabul, when warplanes pounded fighters clashing with US troops and Afghan police on the ground.

One police officer was also killed in the clash, and six US soldiers and five policemen were wounded.

Yonts said all the wounded were in stable condition and that four of the Americans had been taken to a US military hospital in Germany.

Six suspects and a village chief were detained.

Zabul is in a swath of Afghan territory along the border with Pakistan where Taliban-led fighters opposed to the government of US-backed President Hamid Karzai have revived their three-year-old insurgency after a winter lull.