Afghan officials say a U.S.-led coalition air strike has killed 22 civilians in eastern Afghanistan.

District chief Zia-ul-Rehman told reporters the attack happened Friday on a road in the remote district of Nuristan province, near the Pakistani border. He said the civilians were leaving the area, when their vehicles were bombed.

In a statement Friday, the U.S.-led coalition confirmed the air raid but denied any civilians had been killed. The coalition says the air strike was in response to a militant attack on a base and that militants - not civilians - were killed in the air raid.

Afghan President Hamid Karzai has called on foreign troops to minimize civilian casualties. The United Nations says close to 700 civilians have been killed so far this year, after being caught in crossfire between Taliban insurgents and foreign forces.

In a separate incident Friday, Afghan police say a roadside bomb planted by Taliban militants struck a police vehicle in central Ghazni province. At least two officers were killed and several others wounded.

In southern Afghanistan, police say gunmen killed eight officers at a police post in the Panjawi district of Kandahar province on Thursday. Police say the attackers threw a grenade at the post before firing shots

The area is known to be a stronghold for Taliban insurgents, but it is not clear if militants were responsible for this attack. An investigation is under way.

Some information for this report was provided by AFP and AP.