All contact has been lost with a plane carrying 28 passengers in eastern Russia, Russian news agencies said on Tuesday, citing national security services.
The AN-26 aircraft was flying from Petropavlovsk-Kamchatsky to Palana on the Kamchatka peninsula when it stopped sending out reconnaissance signals, Interfax and RIA Novosti agencies said.
Among the 28 people on board were six crew members and one or two children, the agencies said.
Two helicopters have been mobilised to search for the plane, which various sources say may have crashed into the sea or onto the ground near a coal mine near Palana.
Russia has long suffered from a poor reputation for aviation safety, with instances of poor technical maintenance and lax safety regulations.
The last serious accident was in May 2019 when a Sukhoi Superjet belonging to the national airline Aeroflot was forced to land and caught fire on the runway of a Moscow airport, killing 41 people.
In February 2018, a Saratov Airlines AN-148 crashed shortly after takeoff near Moscow, killing all 71 people on board. An investigation determined that human error was the cause of the accident.
Air transport is also subject to often difficult flying conditions in remote areas of the Arctic and the Far East.