A Moscow court has ordered the leader of the Left Front opposition movement, Sergei Udaltsov, placed under house arrest until April 6.
The court's decision came after investigators said they had obtained sufficient evidence to prove Udaltsov was plotting to create mass disturbances in Russia.
On his way into the courtroom, Udaltsov said Russian authorities want to prevent him from engaging in politics.
"I think the Investigative Committee's arguments are baseless, unmotivated, and are just made up of nothing," he said. "They just want to isolate me from public activity. The authorities are tired of me planning and participating in all the mass events, of me speaking publicly...They've had enough."
Judge Artur Karpov sided with investigators and listed the reasons for putting Udaltsov under house arrest.
"Considering the gravity of the offense that Udaltsov is charged with," Karpov said, "and his behavior after the pre-trial restriction upon him; and also considering that if set free he can hide away from justice and continue criminal activity, destroy evidence, or by any other means prevent the investigation of the criminal case; considering his personality data, age, health, and marital status and occupation; and considering that the basis for the current pre-trial restriction -- undertaking not to leave under Articles 97 and 99 of the Criminal Procedure Code of the Russian Federation has changed, according to the investigation officer -- the undertaking not to leave must be replaced by house arrest."
The court ruled Udaltsov would not be able to have contact with anyone except members of his family, his attorneys, investigators, and law enforcement representatives.
Udaltsov is also prohibited from using the telephone, the Internet, or from sending or receiving letters.
Russian investigators say Sergei Udaltsov, Leonid Razvozzhaev, and Konstantin Lebedev had "numerous meetings" last year with foreign citizens while making plans to organize mass disturbances.
The investigators claim Udaltsov and the others met with Georgian citizen Givi Targamadze, who helped them plan violent antigovernment protests on Moscow's Bolotnaya Square in May 2012.
Udaltsov has continually denied the charges that he and other opposition figures were planning mass disorder.
He asked the court not to put him under house arrest, pointing out that he has complied with court-ordered restrictions already placed upon him and cooperated with investigators.
With reporting by ITAR-TASS and Interfax