NATO says six U.S. Marines troops have been killed in a helicopter crash in southern Afghanistan.
A NATO spokesman told Reuters the U.S. military helicopter crashed on January 19.
Earlier reports said there was no insurgent activity in the area at the time of the incident.
NATO said it was investigating the cause of the crash.
The crash came the same day that a suicide bomber killed at least seven civilians outside a crowded gate at Kandahar Air Field, which is used for U.S. and NATO operations in the south.
The Taliban claimed responsibility for that attack, the second suicide bombing in southern Afghanistan in as many days.
The helicopter crash is the worst such incident since August last year when 30 soldiers died when their helicopter came down in eastern Afghanistan.
compiled from agency reports