Amnesty International has classified three activists who are being held in Russia's high-profile Bolotnaya case as "prisoners of conscience."
The decision came as the international watchdog issued a report on October 3 regarding the human rights situation in Russia on the eve of the 2014 Winter Olympics in Sochi.
The head of the Amnesty office in Russia, Sergei Nikitin, told the Interfax news agency that Vladimir Akimenkov, Artyom Savyolov, and Mikhail Kosenko were arrested for "peacefully executing their right to freedom of assembly."
The three men are among at least 12 activists arrested for participating in an antigovernment protest that escalated into violent clashes with police on Moscow's Bolotnaya Square in May 2012.
Activists say the clashes were planned provocations by authorities.
Investigators say the protest was orchestrated by a Georgian politician.
Two participants in the Bolotnaya protest have pleaded guilty and made a deal with investigators.
The trial of 12 others is under way.