Three Afghan policemen have been killed after US-led coalition troops shot at their vehicle by mistake in eastern Kunar province, the US military says.
The coalition troops fired on the unmarked vehicle at a checkpoint on Tuesday, US military spokesman Col Tom Collins told reporters in Kabul.
The policemen were travelling in civilian clothes.
Incidents of friendly fire are relatively rare in Afghanistan, where violence has been rising recently.
Kunar governor Assadullah Waffa said the Americans should apologise for the incident.
The coalition troops opened fire on their vehicle when it approached the checkpoint without slowing down, Col Collins said.
"Coalition soldiers felt that they were in imminent danger so they opened fire on the vehicle," he said.
He said the policemen were armed with rocket-propelled grenade launchers.
Col Collins said coalition forces regretted the incident, in which three policemen were also wounded.
Kunar, one of Afghanistan's most dangerous provinces, has seen a number of attacks and suicide bombings linked to suspected Taleban militants.
Elsewhere, in Helmand province in southern Afghanistan, 20 suspected Taleban militants were killed in a clash with US-led coalition and Afghan forces, the Afghan military said.