A Russian court sentenced prominent opposition figure and journalist Vladimir Kara-Murza to 25 years in a high-security prison Monday on charges of treason. His crime was criticizing Russia’s war in Ukraine. The verdict was the latest in the Kremlin’s increasing crackdown on dissent, and the harshest sentence ever handed to a war critic in the country to date.

Kara-Murza has consistently denied any wrongdoing and denounced the case against him as politically motivated, citing his longstanding opposition to President Vladimir Putin and his criticism of Russia’s flawed elections and the Kremlin’s increasingly draconian policies on free speech and the press.

“I’m in jail for my political views. For speaking out against the war in Ukraine. For many years of fighting against Putin’s dictatorship,” Kara-Murza said during a hearing last week. “Not only do I not repent of any of this, I am proud of it.”

“For a person who has not committed any crimes, acquittal would be the only fair verdict,” he added. “But I do not ask this court for anything. I know the verdict.”

The trial, held behind closed doors, and the unprecedently harsh verdict were both indicative of Moscow’s increasingly intolerant stance on internal dissent. Jailing a Russian journalist for such a long period just for voicing opposition to the war clearly highlighted the Putin government’s rejection of Western condemnation of the war and alleged human rights abuses in Ukraine.

Kara-Murza’s sentencing came as U.S. officials were reportedly granted access to an American Wall Street Journal reporter who was arrested in Russia at the end of March and accused of spying for the U.S. government. A week ago, the Biden administration declared reporter Evan Gershkovich “wrongfully detained” by Russia, and the Journal and Gershkovich’s family, friends and colleagues have all vehemently denied the claim that he was working as anything other than a journalist.

The U.S. has pushed for access to Gershkovich since his arrest, and Russian state media said Monday that U.S. Ambassador Lynne Tracy visited the reporter in Moscow’s Lefortovo prison. There was no confirmation from U.S. officials, who have called for the American journalist’s immediate release.

Ambassador Tracy called, meanwhile, for Kara-Murza’s immediate release, saying in a statement that the sentence was, “another terrible sign of the repression that has taken hold in Russia.”

“The right to have political opinions, or to disagree with the decisions of one’s own government, are fundamental freedoms enshrined in both the Russian constitution and international treaties to which Russia is a party,” she said. “This ruling is an attempt to silence dissent in this country and to make an example of those with the courage to offer an alternative to the policies of the Russian government.”

“Criminalizing criticism of government action is a sign of fear, not strength,” added the ambassador.

Kremlin spokesman Dmitry Peskov refused to comment on the harsh verdict, telling reporters on Monday that the government never comments “on court decisions, and we will not do so this time, either.”

“Twenty-five [year sentence] for words. They don’t even sentence you to that long for murder,” said Ivan Pavlov, one of Russia’s best-known human rights lawyers. “The temperature is rising, the sentences are growing longer. This is indicative of a war.”

Kara-Murza was arrested in April 2022 after making remarks condemning the war in Ukraine abroad in an address to lawmakers from Arizona. Russian prosecutors later alleged that his comments constituted spreading “false information” about the Russian Armed Forces, a violation of a law ushered in just last year by the Kremlin.

He was also accused last summer of cooperating with the Free Russia Foundation, an international organization based in Washington D.C. that’s among many which have been labeled “undesirable” in Russia.

“A quarter of a century is an ‘A+’ for your courage, consistency and honesty in your years-long work,” the journalist’s wife Evgenia Kara-Murza said in a tweet after the verdict was announced. “I am infinitely proud of you, my love, and I’m always by your side.”

Kara-Murza was a target of two poisoning attacks in Russia between 2015 and 2017, both of which Russia’s government denied any role in.

He has lost 48 pounds since he was arrested last April, according to his legal team, and his health has deteriorated swiftly, causing concern that he may not survive a long prison sentence.