A Russian news agency said the downed helicopter was one of three taking part in the operation on Friday.It said fighting erupted at the scene of the crash between fighters and Russian forces.
The air force, in a statement, confirmed the aircraft had come down but said nothing about the cause of the number of casualties.
"At 11:34 (07:34 GMT) while carrying out a mission to transport troops to the south of Shatoi there was an emergency situation which involved a Mi-8 helicopter coming down.
The loss of life would be the largest for Russian forces in a single incident in many months in Chechnya, the site of two devastating wars since 1994 pitting federal forces against separatist fighters.
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