The Federal Investigative Committee (FIC) formally charged Sergei Udaltsov with conspiracy to organize violent protests, after questioning him about the allegations on Friday morning.

Investigators called Udaltsov in for questioning after a pro-Kremlin television station broadcast footage that it said was taken by a hidden camera and showed him discussing his plans with a Georgian parliamentarian.

The 35-year-old leader of the Left Front opposition group denies the charges.

"I'm not guilty of anything: I hold my head high," Udaltsov told reporters as he arrived that the FIC building in Moscow on Friday morning.

Though Udaltsov has not disputed that it was him in the video footage, he says it doesn't show him plotting riots but merely discussing financial support for his opposition movement.

If found guilty, Udaltsov, who is the most prominent of three activists charged in the case, could face up to 10 years in jail. He was not arrested but investigators ordered him to remain in Moscow.

Udaltsov was among the opposition activists who organized street protests amid allegations of fraud during last December's parliamentary election that was won by then-Prime Minister Vladimir Putin's United Russia party. Four months later, Putin was elected for a third term as president.

The president's critics accuse the Kremlin of using legislation and the courts to try to stifle opposition.

pfd/kms (Reuters, dpa, AP)