All four crewmen were killed when a Russian military helicopter crashed south of Moscow today.
Russian news agencies, quoting the air force, said the Mi-8 helicopter was one of a pair flying in the Tula region. The second aircraft landed and searched for the crew members.
Itar-Tass said military prosecutors had launched an investigation into a violation of flight rules. Initial findings suggested the crash was caused by the helicopter icing over, it said.
The crash is the latest in a run of accidents involving Mi-8 helicopters both in Russia and abroad, and comes a week after one of the craft on loan to the UN peacekeeping mission in Sierra Leone crashed into a hillside, killing 24 people.