Five Nato service members have been killed in an apparent friendly fire incident in southern Afghanistan, the international coalition says.
A US defence official said the five were American.
A Nato statement said: “The casualties occurred during a security operation when their unit came into contact with enemy forces. The incident is under investigation.
“Our thoughts are with the families of those killed during this difficult time.”
If confirmed, it would be one of the most serious cases involving coalition-on-coalition fire during the nearly 14-year Afghan conflict. One of the worst came in April 2002 when four Canadian soldiers were killed when an American F-16 dropped a bomb on them near a night firing exercise in southern Kandahar.
A senior police official in southern Zabul province said the soldiers in the latest incident might have been killed when they called for close air support.
Provincial police chief General Ghulam Sakhi Rooghlawanay said: “There was a joint operation by the joint Afghan and foreign forces in Arghandab district of Zabul province on Monday. After the operation was over on the way back, the joint forces came under the attack of insurgents, then foreign forces called for an air support.
“Unfortunately five Nato soldiers and one Afghan army officer were killed mistakenly by a Nato air strike.”
The Taliban claimed responsibility for the attack.
The insurgents have intensified attacks on Afghan and foreign forces ahead of the country’s presidential election run-off on Saturday.