Russian riot police fired tear gas and hit protesters with batons in Bashkortostan on Wednesday after a rights activist was sentenced to four years in a penal colony.
Footage showed supporters of Fail Alsynov clashing with police - some throwing snowballs - near the court.
Alsynov was jailed for inciting ethnic hatred, which he denies.
One protester had a "smashed head", and dozens were detained and injured, monitoring group OVD-Info said.
The trial, and protests, took place in Baymak in southern Russia, near the border with Kazakhstan.
Authorities have opened a investigation against some of those demonstrating under "mass rioting" charges, which carry a maximum sentence of 15 years in prison.
"I advise you to come to your senses and not ruin your life," Bashkortostan's Interior Minister Rafail Divayev warned protesters.
Some reports say there were a few thousand people at the demonstration, which went on for several days in temperatures of around -20C.
Protesters were seen shouting their support for Alsynov, and there are reports that some tried to block the courthouse entrance after the sentence was announced.
Russian investigators said law enforcement officials were among those injured at the protests, and claimed demonstrators used "objects as weapons".
Tear gas was reportedly fired and protesters were seen throwing snowballs at ranks of police behind riot shields.
The activist has now been driven away from the court to applause from supporters, who have started to disperse, OVD-Info said.
Alsynov is accused of insulting migrants at a demonstration against plans to mine for gold, but supporters said it was delayed revenge for his activism in preventing soda mining in what locals consider a sacred place.
He is said to have called Central Asians and Caucasians, who make up most of Russia's migrant population, "black people", considered a derogatory term in Russian.
But he insists the words he used in the Bashkir language mean "poor people" and were mistranslated into Russian. He intends to appeal against the verdict.
He told journalists as he was led away: "I do not accept guilt. I have always fought for justice, for my people, for my republic, so we will see each other again...
"The people came to support me, and I do not know what is going to happen. We did not want this. A huge thank you to all who came to support me."
Alsynov has also in the past criticised military mobilisation in the region as "genocide" of the Bashkir people, a Turkic race closely related to the Tatars which inhabits the southern Ural mountains.
There have been long-running claims that a disproportionately high number of ethnic minorities in Russia are being sent to fight in Ukraine.
Alsynov was a leader of Bashkort, a grassroots movement set up to preserve the ethnic identity of the Bashkirs which was banned as extremist in 2020.
