Afghan border police mistook a group of villagers gathering wood near the Pakistan border as insurgents and opened fire, killing seven civilians, a police official said on Saturday.
All six officers involved in Friday's pre-dawn shooting have been arrested and the incident is under investigation, said General Abdul Raziq, the commander of the border police of southern Afghanistan.
The Afghan-Pakistan border area is a common transit route for both Taliban militants and smugglers, and border police regularly are attacked in the area.
The officers were driving through Kandahar province's Shorabak district before sunrise Friday when they spotted the group of seven men and thought they were about to be ambushed, Raziq said. They started shooting from about 400 yards (meters) away and only discovered when they went to recover the bodies that none were armed, he said.
The officers then confirmed with local residents that the dead were not militants, he added.