NEW YORK (AP) — Vladimir Kara-Murza, who has written columns as a contributor for The Washington Post from his prison cell in Russia, has won the Pulitzer Prize for commentary.

Kara-Murza, 42, is a Russian politician, author and historian who has been imprisoned in Russia since April 2022. He was convicted of treason last year for denouncing the war in Ukraine.

He is serving 25 years, the most severe sentence given to a Kremlin critic in modern Russia. He is among a growing number of dissidents held in increasingly harsh conditions under President Vladimir Putin’s political crackdown.

The prize was awarded to Kara-Murza “for passionate columns written at great personal risk from his prison cell, warning of the consequences of dissent in Vladimir Putin’s Russia and insisting on a democratic future for his country,” according to the Pulitzer announcement on Monday.

Kara-Murza wasn’t available to comment on receiving the award because of his imprisonment, The Washington Post reported. His wife, Evgenia Kara-Murza, thanked the newspaper on Monday “for making sure that the voice of Vladimir is heard,” that he is not forgotten and that his vision is not forgotten.

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The Russian Embassy in Washington didn’t immediately return an email from The Associated Press seeking comment.

Members of Congress last month called for the immediate release of the Russian opposition figure. The charges against Kara-Murza, a dual Russian-British citizen, stem from a March 2022 speech to the Arizona House of Representatives in which he was critical of Russia’s full-scale invasion of Ukraine.

Kara-Murza has survived poisonings twice that he blamed on Russian authorities. He has rejected the charges against him as punishment for standing up to Putin and likened the proceedings to the show trials under Soviet dictator Josef Stalin.

Evgenia Kara-Murza, who lives in the U.S. with their children, has said that her husband has spent months in solitary confinement, a punishment that has become common for Kremlin critics and is widely viewed as designed to put additional pressure on them.

Kara-Murza had been held in a maximum security prison in Siberia, though his supporters said earlier this year that he was no longer there.

Vadim Prokhorov, Kara-Murza’s lawyer, said in a Facebook post that he thinks the best way to congratulate Kara-Murza would be active efforts to get him released and corresponding public demands aimed at the Putin regime.

The Pulitzers were established in the will of newspaper publisher Joseph Pulitzer and first awarded in 1917.