"Fifteen-year-old Artyom Korotkov of Novosibirsk lost consciousness during a fight. Unfortunately, the first aid provided was not sufficient to avert tragedy, and he died," the spokesman told RIA Novosti.
The cause of death has not yet been clarified.
A local police source said an investigation has been launched into the incident on the request of the regional governor, Aman Tuleyev.
Daido Juku, also known as Kudo, incorporates martial arts skills from Kyokushin karate, boxing and wrestling.
Last month, a 19-year old Russian hockey star died of heart failure during a match.
Alexei Cherepanov collapsed on the substitutes' bench after falling on the ice during a Continental Hockey League game in the Moscow Region town of Chekhov. He was taken to a local hospital, where he died later that evening.
Nicknamed the Siberian Express, Cherepanov had played two seasons as a professional, beating in March 2007 the Russia league goal-scoring record for rookies previously held by the legendary Pavel Bure.
He was expected to follow in Bure's footsteps and move to the National Hockey League, having been the New York Rangers' first-round pick in the 2007 NHL draft.