Separately, three soldiers with US-led coalition forces in Afghanistan were killed and a fourth wounded when their vehicle hit a roadside bomb in the west of the country, the headquarters of US forces in the country said Wednesday.

The US-backed government of President Hamid Karzai condemned the killing of the Afghan soldiers by foreign forces and said such incidents could sap the morale of security forces who are fighting a resurgent Taliban movement.

The US military admitted that coalition forces "may have mistakenly killed and injured" Afghan soldiers in the eastern province of Khost and said it was investigating.

Foreign helicopters accidentally targeted the soldiers as they manned a checkpost in an operation to provide security for voters registering for elections, said Colonel Mohammad Gul, a local spokesman for the Afghan army.

"In an international military air strike at 2:00 am... nine members of the Afghan National Army (ANA) were martyred and three others were injured," a defence ministry statement said.

A spokesman for the US-led coalition forces in Afghanistan, Colonel Greg Julian, announced a joint investigation.

"Initial reports from troops on the ground indicate that this may be a case of mistaken identity on both sides," a statement from his office said.

Afghanistan's defence ministry condemned the incident and pledged to bring the "culprits" to justice.

"Such tragic and painful incidents would weaken the morale of the national security forces and could hamper the national army development," it said.

There are about 60,000 international soldiers deployed under NATO and a separate coalition led by the United States in Afghanistan to help defeat an insurgency waged by Taliban and other militants.

The soldiers' deaths are the latest in a series of wayward air attacks which have also killed scores of civilians and police and inflamed public opinion.

In July nine Afghan policemen were killed in strikes called in after troops clashed with police in the southwestern province of Farah, with both sides mistaking the other for Taliban fighters.

Karzai called for a review of regulations for international forces in the country after 90 civilians were killed in US strikes in a western village in August, according to tolls from Afghan and UN investigations.

A US military investigation concluded that at least 33 civilians, including a dozen children, were killed in the strike along with 22 fighters.

The Taliban were in government between 1996 and 2001 and are fighting to take back power in an insurgency that has picked up pace in the past three years.

Late Tuesday, about 100 militants attacked Dih Rahwud district centre in the southern province of Uruzgan sparking a battle that lasted into early Wednesday, police said.

"Our police bravely resisted and killed 35 Taliban whose bodies are left in the area," provincial police chief Juma Gul Hemat told AFP. "Three of our policemen were also martyred and nine others were injured."

The US military later issued a statement saying 55 militants were killed in the battle.

Troops also killed and wounded dozens of "enemies of the people" Tuesday in the southern province of Helmand, the Afghan defence ministry said.

And in the western province of Herat, five police officers were captured by Taliban in an overnight raid on their post, a local official said.

A local Taliban commander claimed the men had surrendered to the rebels but this could not be independently verified.