Protesters in a small town in Russia's central Bashkortostan region clashed with riot police Wednesday after a court sentenced an activist to four years in prison.
Street protests are a rarity in Russia, which has clamped down on dissent since launching its military offensive in Ukraine and has strict anti-demonstration laws.
Crowds of men in the town of Baymak fought with riot police in temperatures hovering around -20 Celsius (-4 Fahrenheit), social media footage showed, with some showing police violently detaining a man lying on the ground.
Police later used tear gas to disperse the protests, an independent rights monitor reported.
Dozens were detained and injured, the OVD-Info group reported, adding that one protestor had suffered a "smashed head".
The local interior ministry said it had opened a criminal case into "mass rioting" -- a crime that carries a maximum penalty of 15 years in prison.
The protests were sparked after a court in the town of around 17,000 people sentenced an eco-activist and campaigner for the protection of the Bashkir language -- Fail Alsynov -- to four years in prison for "inciting hatred".
The ruling was issued behind closed doors.
Alsynov was accused of making a racist comment in a speech to a village council meeting against gold digging. He insists his words were mistranslated from the Bashkir language.
The SOTA opposition Telegram channel showed a video of a handcuffed Alsynov still inside the courtroom after the verdict on Wednesday, protesting his innocence.
"I do not admit my guilt," Alsynov said, vowing to appeal the ruling.
"I always fought for justice, for my nation, for my republic."
According to SOTA, the clashes started after protesters blocked the court building in a bid to try to stop Alsynov from being taken away.
OVD-Info, which monitors protests across Russia, said police had used tear gas to disperse the demonstrators.
Videos shared on social media showed men washing their eyes with water in freezing temperatures outside.
Anticipating a public response, police had on the eve of the verdict warned people not to take part in "illegal public gatherings".
Alsynov's case had already sparked protests of several hundred people in Baymak earlier this week.
The head of the local interior ministry, Rafail Divayev, urged demonstrators to back down on Wednesday.
"Mass riots threaten our country's national security, therefore the punishment under this article is quite serious," the state-run RIA Novosti news agency quoted him as saying.
"I advise you to come to your senses and not ruin your life."
The protests are some of the country's biggest demonstrations since Russia sent troops into Ukraine and escalated a decade-long crackdown on opposition to the Kremlin.
Some of the protests called for the dismissal of the local governor, Radiy Khabirov, who had accused Alsynov of using racist language.
In the speech that resulted in the charges, Alsynov had used two words in Bashkir that were translated into Russian as "black people".
In Russia, the phrase is often used to pejoratively describe people from Central Asia and the Caucasus. Alsynov says he was referring to poor people.
The activist was last year fined for criticising Moscow's offensive in Ukraine online, saying it was not in Bashkortostan's interests.
According to local media, Alsynov called Russia's mobilisation drive a "genocide of the Bashkir people" and said Moscow's offensive "was not our war".
Multiple independent analyses have shown a disproportionately high number of military call-ups and fatalities among Russia's minority national groups, including from Bashkortostan.
