Opposition activist Sergei Udaltsov started a hunger strike on Thursday after being sentenced to 10 days in jail for disobeying the police following a rally against Russian leader Vladimir Putin.
Another Moscow court handed fellow protest leader Alexei Navalny a 1,000-rouble ($34) fine for refusing to leave after attending a separate anti-Putin rally on March 5, the day after Putin won a presidential election.
In a separate case, businessman Alexei Kozlov, the husband of one of the protest organisers, received a five-year jail sentence on fraud charges. He had already served three years in jail, so will serve two more years.
Damn you, court, Kozlov's wife, Olga Romanova, said as the verdict was read out. Dozens of Kozlov's supporters, who say the charges are a punishment for political activities, shouted: Shame on you!
Putin's critics fear he will crack down on his opponents following his election triumph and smother protests sparked by anger at allegations of fraud in the presidential election and in a parliamentary poll won by his party on December 4.
Judge (Diana) Azarova has given me 10 days in custody. As a sign of protest I am declaring a dry hunger strike, Udaltsov said on Twitter after he was sentenced, meaning he will not eat or drink during his detention.
Udaltsov, leader of the Left Front movement, was detained by police on Saturday after addressing a crowd without permission following the end of a rally that had been sanctioned by Moscow city authorities.
He also faces a separate sentence for refusing to go home straight after the rally on Moscow's central Pushkin Square on March 5 at which Navalny, an anti-corruption blogger, was also detained by riot police.
Navalny told reporters after his fine, ordered by Judge Olga Borovkova, that the protests against Putin would continue.
Whether or not Judge Borovkova likes it, there are hundreds of thousands, millions of people in Moscow who are dissatisfied that their votes were stolen. They will continue to go out on to the streets to protest, he said.
($1 = 29.5600 Russian roubles)
(Reporting by Maria Tsvetkova and Nastassia Astrasheuskaya, writing by Timothy Heritage, editing by Steve Gutterman)