Russia has launched a criminal case against protest leader, Sergei Udaltsov, accusing him of provoking "mass unrest" against Vladimir Putin's rule.
The Moscow Times reported the shaven-headed Udaltsov, who has led a series of demonstrations sanctioned by Moscow city authorities, faces a maximum sentence of 10 years jail.
The investigation was opened after authorities studied a pro-Kremlin film, broadcast on state-controlled television, which claimed opposition figures had links to terrorism and were plotting a violent revolution.
The Guardian reported the charges related to claims in the documentary that Udaltsov received cash payments and instructions from an ally of the Georgian president, Mikheil Saakashvili, to cause mass opposition and unrest in Russia.
Media outlets reported the police raided Udaltsov' house and those of his associates, who face the same charges.
Known for his shaven head and hoarse speeches, Udaltsov denies the allegations. He is used to such scrutiny, and in June his home was raided in a similar attempt to crackdown on demonstrations, the BBC reported at the time.
Russia's investigative committee, which answers only to the president, said in a statement on its website today that it had "opened a criminal case against Sergei Udaltsov … on the grounds of … preparing mass disorder".
The committee continued with an ominous warning to any protesters: "Those who think they can organise riots, plan and prepare terrorist attacks and other acts that threaten the lives and health of Russians with impunity, you underestimate the Russian special services' professionalism," the statement said.