Aleksandr Koptsev is charged with ethnically and religiously motivated attempted murder over the 11 January attack.
Judge Lyudmila Zubenko described today's ruling as a preventive measure: "Considering that Koptsev is accused of committing grave crimes and that he has no particular occupation, the court has every reason to believe that, if released, Koptsev may escape from investigation and trial and may continue to engage in criminal activity."
Koptsev is accused of stabbing and wounding eight men during evening prayers at the central synagogue.
The attack has been widely condemned by Russian political and religious leaders. Jewish groups have asked for reinforced security around synagogues.
(Interfax, RIA-Novosti, AP)
