A Moscow court set the date Tuesday for a new trial of imprisoned Russian opposition leader Alexei Navalny that could keep him in prison for decades.

The Moscow City Court held a preliminary hearing behind closed doors to discuss technical issues related to the trial of the Kremlin's arch foe before it begins on June 19.

Navalny's spokeswoman, Kira Yarmysh, said that the trial will be held at a maximum security prison 250 kilometers (150 miles) east of Moscow where Navalny is serving a nine-year sentence for fraud and contempt of court.

Navalny, 47, who exposed official corruption and organized major anti-Kremlin protests, was arrested in January 2021 upon returning to Moscow after recuperating in Germany from nerve agent poisoning that he blamed on the Kremlin.

Navalny has said that the new extremism charges which he rejected as “absurd” could keep him in prison for another 30 years. He said an investigator told him that he would also face a separate military court trial on terrorism charges that could potentially carry a life sentence.

The new accusations come as Russian authorities are conducting an intensified crackdown on dissent amid the fighting in Ukraine, which Navalny has harshly criticized.

Navalny's supporters marked his birthday on Sunday by holding pickets and demonstrations, and more than 100 people were arrested.