A Moscow court on Wednesday dismissed a prominent Russian opposition figure's appeal of his 8 1/2-year prison sentence for criticism of Russia's actions in Ukraine.

Ilya Yashin was convicted in December of spreading false information about the military, which was made a criminal offense after Russian President Vladimir Putin sent troops into Ukraine.

The charges against him stemmed from a series of online posts discussing atrocities in Bucha, a town outside Ukraine's capital where dead civilians were found in the streets and a mass grave after Russian troops withdrew.

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During his trial last year, Yashin argued that a livestreamed YouTube video in which he talked about Ukrainians being killed in Bucha cited official Russian sources along with Ukrainian statements to give his audience an objective view.

"I will not renounce the truth behind bars," he said, emphasizing that he considered it his duty to tell the truth.

Yashin, one of the few Kremlin critics to have stayed in Russia after Putin launched the military action in Ukraine, participated by video link in Wednesday's Moscow City Court hearing on his ultimately unsuccessful appeal.

Ilya Yashin

Russian opposition activist Ilya Yashin is seen on a tv screen from a video link provided by the Russian Federal Penitentiary Service in a courtroom of the Moscow City Court during a hearing on his appeal of his prison sentence, in Moscow, Russia, on April 19, 2023.  (AP Photo/Alexander Zemlianichenko)

International human rights groups have denounced the sentence as a mockery of justice and called for Yashin’s immediate release.

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Before his sentencing, Yashin addressed Putin directly, urging him to "immediately stop this madness, recognize that the policy on Ukraine was wrong, pull back troops from its territory and switch to a diplomatic settlement of the conflict."

Asked at the time about the Dec. 8 verdict, Putin replied that Yashin’s lawyers could appeal it.

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Russian authorities have repeatedly used the law on discrediting the military to stifle dissent. 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.