A court in Moscow has sentenced a prominent opposition activist to 10 days in jail for "refusal to follow police instructions" on March 10 when he tried to hold an unsanctioned march to Moscow's Pushkin Square.
The coordinator of the Left Front opposition movement, Sergei Udaltsov, announced a hunger strike to protest the verdict.
Also on March 15, another leading opposition activist, Aleksei Navalny, was fined for violating a law against mass gatherings.
Navalny was fined 1,000 rubles ($34) after a Moscow judge found him guilty over the "refusal of some protesters to leave a Navalny-organized gathering on Moscow's Pushkin Square on March 5 after the time allowed by local authorities was over."
Navalny told journalists that he planned to appeal the decision.
"The legal system, the legal machinery is set up in such a way that it bars citizens from participating in legal protests, from gathering peacefully and without arms, as is guaranteed by the constitution," Navalny said.
"Well, we have been working in these conditions for the past five years, and apparently we will continue to do so."
Aleksei Navalny talks to the crowd at the March 5 anti-Putin rally on Pushkinskaya Square in Moscow.
The trials are the latest since flawed elections for a new State Duma in December mobilized swaths of society angry over Putin's grip on power and carefully orchestrated return to the Kremlin, sealed with the March vote.
A Putin spokesman has praised the "high level of professionalism" when police arrested hundreds of demonstrators
at a March 5 protest in Moscow. Hundreds more were detained the same evening in St. Petersburg.
Opposition leaders have vowed to continue staging mass rallies against Putin's leadership.
With ITAR-TASS and Interfax reporting