An Antonov-26 plane with six people onboard has disappeared from radar in Russia's Khabarovsk region, according to the nation's emergency services ministry.
"The An-26 plane with six crew members on board disappeared from radars 38 kilometres [23 miles] south-west of Khabarovsk," a spokesman for emergency services said.
The plane was conducting the flight to test its communication equipment.
A Mi-8 helicopter of the Russian Federal Air Transport Agency has been sent for a search operation, which is being hampered by poor weather conditions and a lack of daylight.
According to preliminary information, the incident may be blamed on bad weather, the spokesman added. However, the version of a technical fault of the aircraft is also not excluded.