Russian left-wing activist Sergei Udaltsov has been charged with justifying terrorism on social media, the state-run news agency RIA Novostireported Thursday, citing an anonymous law enforcement source.Udaltsov, who heads the socialist group Left Front, has been a vocal participant in anti-Kremlin demonstrations dating back to mass rallies held in 2012. In 2014, he was sentenced to four-and-a-half years in prison for organizing protests that resulted in clashes with police on the eve of President Vladimir Putin’s 2012 inauguration.

He was released in August 2017.Early Wednesday, Udaltsovwrote on the messaging app Telegram that police were trying to break into his home.The activist's lawyer Violetta Volkova told the state-run TASS news agency that authoritiesseized his personal electronic devices.She did not say which of Udaltsov's social media posts might have led authorities to charge him with justifying terrorism.Officials from Russia's Investigative Committee, which probes major crimes, then took the activist in for questioning, Volkova told Interfax. Citing an anonymous source familiar with the matter, the news agency reported that investigators will decide whether to place Udaltsov in custody after questioning.He could face up to seven years in prison if found guilty of justifying terrorism.