The trial of 12 participants in last year's violent protest on Moscow's Bolotnaya Square has started in the Russian capital.
The defendants have been charged with taking part in mass unrest.
Investigators say 82 police officers were injured during the violence and the overall damage to the city was estimated at 28 million rubles ($850,000).
Opposition activists say the clashes that occurred were the result of planned provocations by authorities.
One participant in the protest, Maksim Luzyanin, was sentenced to 4 1/2 years in jail in November.
Last week, the coordinator of the Left Front movement, Sergei Udaltsov, and a Russian opposition lawmaker's aide, Leonid Razvozzhayev, were officially charged with the preparation and the organization of the mass unrest, which investigators say was orchestrated by a Georgian politician.
Based on reporting by ITAR-TASS and Interfax