Sergei Krivov, a participant in the protest on Moscows Bolotnaya Ploshchad in 2012, has been released from prison, activist Maria Arkhipova announced Friday on Facebook.

Krivov participated in the famous March of Millions on May 6, 2012. The opposition protest against electoral fraud and corruption resulted in clashes with the police. More than 30 people were subject to criminal investigations, with 11 serving prison terms.

Krivov was charged with participating in riots and violence against law enforcement officers. In 2014, he was sentenced to four years imprisonment.

Arkhipova, a representative of the May 6 Committee, a group lobbying for the release of the protesters, announced Krivov's release in a statement on Facebook.

Sergei Krivov has been freed and will arrive in Moscow by train tomorrow morning, she said Friday.