A Russian court on Monday convicted top opposition figure Vladimir Kara-Murza Jr. of treason for publicly denouncing Moscow’s war in Ukraine and sentenced him to 25 years in prison as part of the Kremlin’s relentless crackdown on critics of the invasion.

The political activist and journalist, who twice survived poisonings he blamed on Russian authorities, has rejected the charges against him as punishment for standing up to President Vladimir Putin and likened the proceedings to the show trials under Soviet dictator Josef Stalin. Human rights organizations and Western governments denounced the verdict and demanded his release.

Kara-Murza reacted calmly as the judge read the verdict and sentence in a quick monotone. His lawyer, Maria Eismont, later quoted him as telling her: “My self-esteem has risen: I realized that I have done everything right. Twenty-five years is the highest appraisal that I could get for doing what I did and what I believed in, as a citizen, a patriot and a politician.”

Kara-Murza’s wife, Evgenia, who lives in the U.S. with their three children, tweeted after the verdict: “A quarter of a century is an ‘A+’ for your courage, consistency and honesty in your years-long work. I am infinitely proud of you, my love, and I’m always by your side.”