Russian opposition leader Alexei Navalny Tuesday said he faces new criminal charges and a potential for fifteen additional years in Russian prison if found guilty. Navalny is already serving a nine-year sentence after a Moscow court found him guilty of fraud and contempt in March.

Navalny, a longtime critic of President Vladimir Putin, wrote on his Instagram that a Russian investigator filed new charges against him only eight days after his nine-year sentence began. The investigator charged Navalny with creating an extremist group to incite hatred towards Russian officials and oligarchs. According to Navalny, the new charges could add an additional fifteen years to his prison sentence.

Navalny has been in police custody since he returned to Russia in January 2021. Navalny had been in Germany recovering from a nerve-agent attack, which he asserts was carried out by the Kremlin. At the time, Navalny was given a two-and-a-half year sentence for violating parole. Then in March 2022, Navalny was sentenced to an additional nine years for fraud and contempt of court.

The Kremlin’s actions against Navalny are a part of an ongoing crackdown on Russian opposition. The Kremlin has moved to suppress opposition efforts in Russian politics and media.