"Reinforcements were called in and three defence ministry helicopters arrived. One helicopter, according to preliminary data, was shot down while landing," he said.


However, Ramzan Kadyrov, the Chechen president gave another version of the crash.


"The cause of the catastrophe, according to information from the scene, was a technical failure," RIA Novosti quoted him as saying.


The air force, in a statement, confirmed the aircraft had come down but said nothing about the cause or 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.