A Russian court sentenced Udaltsov, the leader of the Left Front, to house arrest for allegedly plotting against the state. Russia's state-run news agency RIA Novosti states prosecutors were fearful Udaltsov may be able to continue an anti-government campaign if he remained free.
Udaltsov is confined to his home and barred from contacting anyone apart for investigators, legal counsel and family members. The opposition leader told the court before his sentencing that he wasn't evading authorities.
"Even when I get up in the morning, I check if anyone from the investigative committee has called," he was quoted by the Russian news agency as saying.
Udaltsov was tied to a plot "aimed at organizing mass disturbances in Russia" with Georgia leader Givi Targamadze.
Targamadze was one of the leaders of the Rose Revolution in Georgia in 2003.Udaltsov denies the allegations, though he's facing at least 10 years in prison for allegedly plotting against the government.
Russian President Vladimir Putin in November signed a measure that expands the definition of treason to include activity that poses a threat to Russia's "constitutional order, sovereignty and territorial and state integrity."