Yevgeny Roizman, a prominent Kremlin critic and popular former mayor, went on trial on Wednesday over accusations of discrediting the Russian army over the Ukraine offensive.
In 2013, Roizman, 60, became Russia's highest-profile opposition mayor and held the position in the Urals city of Yekaterinburg for five years.
He is Russia's last prominent opposition figure who is still in the country and not behind bars.
Roizman, who openly denounces President Vladimir Putin and his offensive in Ukraine, has said he knows he could go to prison at any moment. He is a hugely popular figure in Yekaterinburg and beyond and a friend of jailed Kremlin critic Alexei Navalny.
In August 2022, authorities opened a criminal probe against Roizman who stands accused of "discrediting" the Russian army in comments about Moscow's military intervention in Ukraine.
Dressed in blue jeans and a white T-shirt, Roizman pleaded not guilty at the start of the trial in Yekaterinburg, according to a live YouTube broadcast of the hearing.
Asked by the judge if he admitted his guilt, Roizman said "no".
Roizman has a penchant for crude language and has peppered Twitter with swear words to mock officials, much to the delight of his supporters.
The Russian public has been reeling from a historic crackdown on dissent as Moscow presses ahead with its military intervention in Ukraine.
All top opposition figures are either in prison or in exile.