Russian military authorities temporarily halted flights by Mi-8 military transport helicopters on Thursday after a crash injured three pilots, authorities said. Within a few hours, a civilian Mi-8 crashed, killing four people and injuring another two.
The first incident involved a military Mi-8 that crash landed near the eastern city of Khabarovsk and injured three pilots, the Interior Ministry's regional branch said.
Later on Thursday, four died when another Mi-8 helicopter used for civilian purposes crashed near the Siberian oil center of Nefteyugansk, The AP reports.
Four of the six crew members, who were providing aerial surveillance of oil pipelines, were killed, spokesman Sergei Vlasov said. The other two were hospitalized, one in critical condition.
The military Mi-8 helicopter ran into trouble an altitude of 1,200 meters (3,940 feet) when its tail propeller malfunctioned. Eight parachutists bailed out and the chief pilot crash landed the helicopter, air force spokesman Alexander Drobyshevsky was quoted as saying by the Interfax news agency.
Air force commander Vladimir Mikhailov ordered a temporary suspension of Mi-8 helicopter flights until the cause of the accident is established, Drobyshevsky said. The ban applies only to military Mi-8s.
Russian NTV television showed the wrecked helicopter on grass next to a railway track with fire engines parked nearby. "The three pilots are in hospital," said Alexander Kalyaka, acting head of the Russian air force in the region.
The Russian air force has several hundred Mi-8 helicopters in use. The craft, which can carry 24 people and can also be used as a gunship, was first designed in the 1960s and thousands have been manufactured and been widely exported.
Mi-8 helicopters crashes are frequent in Russia, and are often blamed on poor maintenance of the aging Soviet-era craft.
The United States and NATO are conducting provocative activities both in airspace and waters of the Black Sea, Russian Defense Minister Sergei Shoygu said