Riot police fired tear gas, flash grenades and used batons to disperse demonstrators in Russia’s Bashkortostan region after a local activist was sentenced on Wednesday to four years in prison.

Videos showed supporters of Fail Alsynov clashing with police near the court where he had been convicted of inciting ethnic hatred, according to Russian state media outlet RIA Novosti.

Bashkortostan’s Ministry of Internal Affairs called the demonstrations an “unauthorized rally” and said police have begun investigating “mass unrest,” in a post on Telegram.

Thousands of demonstrators gathered outside a public building in the remote town of Baymak, with some waving the blue, white and green flag of Bashkortostan region, which neighbors Kazakhstan.

Protesters could be heard chanting “Freedom,” in a video posted on public Telegram channels and shared by OVD-Info. In another, protesters were seen throwing snowballs at police holding riot shields. Chants of “shame” could be heard after police fired tear gas.

Some social media accounts are reporting that internet connection was restricted in the area of the gathering.

Alsynov spoke at a rally in spring 2023 against the mining of a mountain considered to be sacred to the Bashkir people, a Turkic ethnic group concentrated in Bashkortostan and closely related to the Tatars.

The protests in Bashkortostan have become some of the most significant in Russia since its full-scale invasion of Ukraine nearly two years ago.

OVD-Info said Alsynov “faces a four-year sentence for speaking out against the Kremlin’s invasion of Ukraine.”