Moscow (CNN) -- Three Russian opposition leaders were arrested Saturday "for disrupting public order" after an unsanctioned opposition event in downtown Moscow, police said, according to Ria Novosti.
Sergei Udaltsov, the 35-year-old leader of the Left Front movement, has helped organize mass protests against President Vladimir Putin's rule, the state news outlet reported.
It identified the other two arrested opposition leaders as Alexei Navalny and Ilya Yashin.
The charges against Udaltsov can be traced to news footage broadcast this month by NTV. The pro-government channel said the clip showed Udaltsov and two fellow Left Front members meeting with a Georgian politician, Givi Targamadze, to discuss how to overthrow Putin.
Udaltsov has said the footage is fake.
He was taken into custody as he walked with supporters and journalists on Myasnitskaya Street, Ria Novosti said. He was charged Friday with plotting mass disorder, for which he could be sentenced to as many as 10 years in prison if found guilty.
The other two men allegedly in the video -- Leonid Razvozzhayev and Konstantin Lebedev -- are in custody awaiting trial, Ria Novosti reported.
The opposition has held a number of unsanctioned events in support of political prisoners, the news agency said. In the events, people stand 50 meters apart in a line stretching from the state security FSB headquarters on Lubyansky Proezd to the Investigative Committee Headquarters on Tekhnichesky Pereulok.
Also Saturday, tycoon Mikhail Prokhorov announced that he has joined the Civic Platform party he founded in July and will devote himself full-time to politics, Ria Novosti reported.
Prokhorov, 47, told the party convention that he is a candidate to lead the party. He had previously said he would not join the party or lead it, Ria Novosti reported.
He owns control of the New Jersey Nets basketball team.