The statement, which did not elaborate on what had caused the crash, offered no details on the nationalities of the killed troops.

"ISAF is still in the process of reviewing the circumstances to determine more facts," ISAF said on Saturday.

Foreign forces casualties have fallen in the past few months, as US-led forces start to wind down operations ahead of a year-end deadline to leave Afghanistan.

The United States has been at odds with President Hamid Karzai who has refused US entreaties to sign a bilateral security agreement that would permit about 8,000 US troops to remain in the country after the formal US withdrawal at the end of the year.

Afghan activists say the security treaty between Washington and Kabul will pave the way for a prolonged US military presence in the war-ravaged country.

Afghan political figures have also heaped scorn on US-led forces for committing unforgivable crimes against Afghan women and children since invading the country in 2001.

RA/MB