ISAF gave no further details, saying in a statement that it was still reviewing the circumstances of the crash. The nationalities of the soldiers are unknown at this stage.
Afghan officials said the helicopter had come down in Kandahar province because of a mechanical failure.
Foreign forces are due to hand over responsibility for security to their Afghan counterparts at the end of 2014.
Fatal incidents involving foreign troops have declined as they prepare for the withdrawal.
However, such crashes have been relatively frequent over the years because coalition forces depend heavily on air transport.
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