Russian investigators said they searched the homes of opposition leaders Taisia Alexandrova, Anna Kornilova and Yury Nabutovsky, who were questioned in relation to an investigation into the activities of protest leader Sergei Udaltsov.
A statement from investigators published by state-run news agency RIA Novosti said they found 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 2003. Nikolai Patrushev, the head of the Security Council of Russia, this week said the Kremlin is keeping a close eye on potential "color revolutions" in former republics of the Soviet Union.
Udaltsov told the Russian news agency he's never met the three opposition leaders under investigation.
Several opposition supporters have been detained in the country amid growing frustration with President Vladimir Putin's grip on power. Udaltsov, leader of the opposition Left Front movement, is under investigation for allegedly plotting against the state.