MOSCOW – All 10 crew on board a Russian military plane that crashed during a training exercise were believed to have died in the accident, a source close to the inquiry said Saturday.

Russian authorities confirmed the crash on Friday involving a Tupolev-142 plane in the eastern Khabarovsk region.

"According to information on the air disaster... all the crew members have probably been killed," said the source, quoted by the Interfax news agency.

"Rescue operations are ongoing at the scene and the chances of finding survivors are slim," the source added.

The aircraft was crossing a lake when radio contact was lost, the Defense Ministry was quoted as saying by news agencies.