The military alliance said police "successfully repelled" an attack on a school, clinic and the district governor's building in Dahanah-ye Ghori on Tuesday, killing several fighters, but that the police checkpoint had been overrun.

"During the attack, insurgents overran a police checkpoint and killed the police officers by cutting off their heads," it said.

The attack took place as Hamid Karzai, the Afghan president, hosted an international conference during which he said he hoped that the country's forces would be able to take over responsibility for security by 2014.

He suggested that foreign troops would be able to leave some areas by as soon as the end of the year.

Despite the number of foreign troops in Afghanistan rising to about 150,000, the Taliban continue to stage deadly attacks against government, military and civilian targets.