The reports said the Boeing 737 belonging to Tatarstan Airlines crashed about 7:20 p.m. local time (1520 GMT) on Sunday. There were no immediate indications of what may have caused the crash.
Kazan is about 450 miles east of Moscow.
The ITAR-Tass news agency quoted a local representative of the Emergencies Ministry, Irina Rossius, as saying preliminary information indicated 44 people were aboard and all had died.
The flight originated in Moscow.