U.S. Secretary of State Antony Blinken said Tuesday he is “troubled by dubious new charges” against Russian opposition leader Alexey Navalny, who went on trial Tuesday in a penal colony outside of Moscow.

Navalny is accused of embezzlement and contempt of court. If convicted, he could face up to 15 more years in prison. 

“Navalny and his associates are targeted for their work to shine a light on official corruption,” Blinken tweeted. He added a call for Russian authorities to release Navalny “and end their harassment and prosecution of his supporters.” 

The Kremlin critic was arrested in January 2021 and convicted of violating his parole by spending several months in Germany recovering from a poison attack. He was sentenced to two-and-a-half years in prison.

At his new trial, Russian investigators say Navalny embezzled money donated to his FBK anti-corruption political organization. The contempt of court charge stems from Navalny allegedly insulting a judge during a previous trial. 

“It is just that these people, who ordered this trial, are really scared,” Navalny, 45, said during the hearing. “(Scared) of what I say during this trial, of people seeing that the case is obviously fabricated.”  

Navalny adamantly denies the accusations and calls them politically motivated.  

“I am not afraid of this court, of the penal colony, the F.S.B., of the prosecutors, chemical weapons, Putin and all others,” Navalny said in court, according to a video of his statement. “I am not afraid because I believe it is humiliating and useless to be afraid of it all.”

Navalny’s allies have denounced the case, and his lawyer says it is an attempt by the Kremlin to silence him.

“We believe the persecution of Navalny is illegal, is distinctly political in nature, and aimed at discrediting and removing him from political activity,” lawyer Olga Mikhailova said, according to Agence France-Presse. 

A longtime rival of Russian President Vladimir Putin, Navalny has accused the president of enrichening himself as well as other government officials through corrupt measures. His attempt at running in the 2018 presidential elections only aggravated his relations with the Kremlin. 

As of a few months ago Navalny and his associates have been added to a state registry of extremists and terrorists by Russian officials.