Investigators earlier said Leonid Razvozzhayev turned himself in and confessed to orchestrating riots. His supporters insist he was kidnapped abroad, smuggled back to Russia and tortured into confessing. A video published on a news website showed Razvozzhayev shout to reporters about this, but investigators deny the allegations.
Russia's Investigative Committee on Tuesday formally brought charges against Razvozzhayev, who now faces up to 10 years in prison. The opposition activist's supporters have been picketing the investigators' office for several days in protest.
Authorities also are pursuing criminal cases against Sergei Udaltsov and Konstantin Lebedev, relying on the same alleged hidden camera footage aired this month by a Kremlin-friendly TV channel.