Six U.S. soldiers were killed in a plane crash in southern Afghanistan on Tuesday, NATO said, the largest death toll in a single incident to hit the international force in months.
"The cause of the crash is under investigation, however initial reporting indicates there was no enemy activity in the area at the time," a NATO statement said.
The NATO-led ISAF military command declined to say where the soldiers were from, which province they died in or how exactly the crash occurred.
Aircraft crashes are not uncommon in mountainous Afghanistan.
The worst such incident was in August 2011, when the Taliban shot down a transport helicopter, killing all 38 people on board including 25 U.S. special operations forces.
About 84,000 NATO-led troops are serving in Afghanistan, including about 60,000 from the United States. That number is expected to be reduced to about 10,000 by 2015.