MOSCOW — A Moscow district court ordered Sergei Udaltsov, a prominent opposition leader, to be placed under house arrest on Saturday, in one of the most assertive legal measures to date against a leader of the anti-Kremlin protests that began more than a year ago.
Mr. Udaltsov, the leader of the radical socialist Left Front movement, faces a charge of conspiracy to incite mass disorder, under a statute that can bring a maximum sentence of 10 years in prison. According to Saturday’s ruling, he may not leave his house, use the Internet, receive letters or communicate with anyone outside his family and legal team until April 6, the current date for the end of the investigation of his case.
The ruling seemed to signal a new stage in the government’s effort to bring criminal cases against well-known critics of President Vladimir V. Putin. Though most of the well-known protest leaders have served short sentences for administrative violations, and several are the subject of criminal inquiries, none had yet been held on criminal charges.
Mr. Udaltsov, a passionate public speaker and the great-grandson of a prominent Bolshevik, has stood out among the Moscow protesters, many of them middle-class Russians who distance themselves from calls for revolution. He was also one of the few to focus early on economic issues relevant to Russians outside large cities.
Speaking with journalists outside the courtroom, Mr. Udaltsov said he had broken no laws and called the decision “a political order against me because my public actions anger the government.”
“All the reasons being offered as evidence were already perfectly clear to them in October, when I was first placed under a travel ban,” Mr. Udaltsov said. “Nothing has changed.”
During Saturday’s hearing, prosecutors also claimed that Mr. Udaltsov had threatened to attack his wife, Anastasia, and that she at one point had fled to Ukraine with their children. A judge refused to allow Ms. Udaltsova to testify in court on Saturday, but she told the Novaya Gazeta daily newspaper that the accusation was “a total lie.”
Mr. Udaltsov has been accused of attacking the police and rioting at an anti-Putin demonstration that ended in clashes last May, and of attempting to organize anti-government riots in cities across Russia.
He has been under a travel ban since October, but prosecutors said that he had gone outside Moscow and continued to lead public rallies while under investigation. A statement from investigators charged that Mr. Udaltsov “has not lived at his registered address for a long time, his mobile telephone is often switched off, making it difficult to summon the accused to investigators.”
The statement also said Mr. Udaltsov “does not inform the investigation of his factual location.”
Saturday’s ruling came at the request of Russia’s powerful Investigative Committee, which has recently revived several stalled criminal investigations against Russian opposition leaders including Aleksei Navalny, a popular blogger and corruption whistle-blower accused in December of stealing hundreds of thousands of dollars in a business swindle.
Mr. Udaltsov, in his closing arguments, told the judge that if he was placed under house arrest, he would like the state to afford him a 13-room apartment, a cook and a maid — a reference to the house-arrest conditions reportedly granted to a Defense Ministry official currently facing corruption charges.
This article has been revised to reflect the following correction:
Correction: February 9, 2013
An earlier version of this article incorrectly stated Sergei Udaltsov’s family ties. He is the great-grandson of a prominent Bolshevik, not the grandson.
