In a new sign of a widening crackdown on Russian opposition, a criminal investigation has begun into leftist leader Sergei Udaltsov and several other opposition activists for allegedly plotting mass riots.
Mr Udaltsov, a 35-year-old, shaven-headed Communist who wore a Stalin T-shirt for his wedding, has been one of the most recognisable faces of last winter's anti-government protests in Moscow, which were peaceful.
Investigators searched his and his parents' apartments in Moscow.
A documentary on NTV, a channel seen as a propaganda arm of the Kremlin, showed what it says was footage of the Left Front leader meeting with officials from neighbouring Georgia to discuss raising money for protests against president Vladimir Putin, and plans for organising riots in Moscow.
The state Investigative Committee said that it would pursue criminal cases against not only Russians, but also citizens of Georgia and other unspecified countries.
"Once their involvement in the preparation of criminal acts is established, they will be subject to criminal liability under Russian law and the norms of international law, and will be issued with international arrest warrants," the committee said.
Mr Udaltsov said he has met "a great number of people" recently to discuss fundraising, but all of his efforts and intentions are legal. He has insisted the footage presented in the documentary has been doctored.
The Investigative Committee said that it had carefully studied the footage and said it was not tampered with.
Human rights activist Lev Ponomarev said that a "broad crackdown on the opposition is very dangerous for this country" and said that early morning searches reminded him of secret police tactics in the 1930s in the Soviet Union.
The Russian Communist Party, which forms the largest opposition faction in parliament, has supported Mr Udaltsov, dismissing allegations against him as nonsense.