A NATO plane crashed in Afghanistan on Saturday killing four service members, the coalition said, adding that early reports suggested the aircraft was not brought down by insurgents.
The plane crashed in the south of the country, according to a statement from NATO's International Security Assistance Force.
"The cause of the crash is under investigation, however initial reporting indicates there was no enemy activity in the area at the time of the crash," it said.
Most international soldiers in southern Afghanistan are from the United States, but the nationality of the dead was not released in line with coalition policy.
There was no immediate claim of responsibility from the Taliban, who earlier Saturday announced the start of their annual "spring offensive" vowing a nationwide series of attacks as NATO troops withdraw from Afghanistan.
Aircraft crashes are fairly frequent in Afghanistan, where the 100,000-strong international mission relies heavily on air transport as it battles the insurgency across the south and east of the country.
Earlier this month, two US troops were killed when a NATO helicopter crashed in the eastern Afghanistan, while five US troops died in the southern province of Kandahar in May when their helicopter came down during a heavy rainstorm.