Udaltsov, the leader of the opposition Left Front, was arrested last year. According to the independent news site Mediazona, the charges against him stem from a post Udaltsov published on social media.
In the post, Udaltsov expresses support for another group of Russian activists accused of being a terrorist organization. Several of them were sentenced this fall to prison terms of between 16 and 22 years.
Udaltsov denies the charges against him, claiming they are fabricated. He calls the accusations “shameful” and threatens a hunger strike.
Udaltsov will serve his sentence in a maximum-security penal colony, according to the court. He previously served more than four years in prison for organizing a demonstration against Putin, but was released in 2017.
