A Russian military jet has crashed while trying to land and the fate of its two crew member is unknown, the Defence Ministry said.
A spokesman said the Su-24 bomber crashed as it was approaching its base in the southern Volgograd region during a regular training mission and a search was under way to locate the crew.
The Russian air force has temporarily grounded its Su-24 fleet pending an investigation into the crash, according to a Defence Ministry statement carried by Russian news agencies.
The twin-engine Su-24 has been a mainstay of both the Soviet and Russian air force since the 1970s.