Alexei Navalny, who led the biggest protests against President Vladimir Putin since he took power in 2000, was sentenced to five years in jail for theft on Thursday.
Navalny, a blogger who became a hero to the country's growing urban middle class, denied all charges and supporters had called the charges politically motivated. The move is widely viewed as a harsh new stage in Putin's Soviet-style crackdown on domestic dissent.
The BBC reported that before he was handcuffed and led away, Navalny urged his supporters to continue his anti-corruption struggle, tweeting: "Don't sit around doing nothing."
The United States and European Union expressed concern over the conviction, saying it raised questions about the rule of law in Russia and Putin's treatment of opponents.
State prosecutors had asked the court to jail Navalny for six years on charges of organizing a scheme to steal at least 16 million roubles ($494,400) from a local timber firm when he was advising the Kirov region governor in 2009.
But even a five-year sentence means he will not be able to run in the next presidential election in 2018 or for Moscow mayor in September as Navalny had planned.
Thousands of Russians took to the streets on Thursday, demanding Navalny's freedom and calling for the ousting of the president, Vladimir Putin. Dozens were detained, The Guardian reported.
UPDATE – 4 P.M. EST: Arrests and clashes between the protesters and police have escalated.
