The US military said on Wednesday that about 20 suspects and one Afghan police officer were killed in a bloody battle in the mountains of southeastern Afghanistan on Tuesday.

Six US soldiers were also wounded in Tuesday's clash, which occurred in Dehchopan district of Zabul province, the military said in a statement.

It said helicopters and fixed-wing aircraft joined the fight against a group of about 25 insurgents.

The casualty figures were still preliminary, the statement said, adding that five Afghan police officers were wounded, and six insurgents were detained and questioned.

It said the wounded US soldiers were in stable condition, and two had returned to duty. The four others were to be flown to a US military hospital in Germany for treatment.

Zabul lies 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.