Aleksandr Koptsev had been convicted of attempted murder and sentenced to 13 years in prison for stabbing nine worshippers with a hunting knife.
Koptsev's lawyers had appealed the sentence, arguing their client was mentally unstable.
Prosecutors also filed an appeal, asking for the inclusion of a charge -- dropped from the original trial -- of inciting interethnic hatred.
A spokesman for the Supreme Court said the reasoning for today's decision would be made public at a later time.
Russia has seen a wave of attacks in recent months targeting religious and ethnic minorities. Activists have accused authorities of failing to prosecute hate crimes.
(ITAR-TASS, Interfax, AP)
Epidemic Of Hate
Yusuf Sultonov, whose 9-year-old daughter was beaten and stabbed to death in St. Petersburg on February 9, 2004 (TASS)
EXTREMISM ASCENDANT: More than half of Russians have xenophobic views, according to a report published in August 2005. In the report, rights groups say that -- despite progress in some areas -- racism, xenophobia, and anti-Semitism remain rife in Russia. But what worries watchdogs most are recent moves by nationalist-patriotic movements to form paramilitary groups....(more)
ARCHIVE To view an archive of all of RFE/RL's coverage of Russia, click here.
For a regular review of civil-society developments throughout RFE/RL's broadcast region, subscribe to "RFE/RL (Un)Civil Societies."
RFE/RL IN RUSSIAN: Visit RFE/RL's Russian-language website, featuring news, analysis, features, streaming audio, and more in Russian, courtesy of RFE/RL's Russian Service.