MOSCOW, Russia - Russia on Monday placed four men in pre-trial detention for taking part in rare protests that shook the Urals region of Bashkortostan, a republic with a large ethnic minority.

Thousands took to the streets of the small town of Baymak last week, and some clashed with riot police.

The protests were to support Fail Alsynov, an activist for the protection of the Bashkir language who was sentenced to four years in jail for "inciting hatred."

A court in the regional capital of Ufa ruled to keep the four men in detention until March 17.

"The Soviet district court chose a preventative measure for four participants in an unauthorised rally in the city of Baymak," said a court statement.

Three suspects -- Azat Mirzin, Dayan Valeyev and Rayat Davletbayev -- are accused of taking part in "mass riots" and using violence against law enforcement.

A fourth man, Vilyur Karachurin, was accused of only taking part in "mass riots".

Charges of organising or joining illegal demonstrations deemed by authorities to be riots carry a maximum penalty of up to 15 years in prison.

Rights group OVD-Info, which monitors arrests in Russia, said authorities have also opened dozens of lesser administrative cases, accusing demonstrators of joining unsanctioned rallies.

A court in Baymak, 1,400 kilometres (870 miles) east of Moscow, last week sentenced several people to up to 15 days in prison for disobeying police orders during the protests.

Police used tear gas to disperse thousands of protesters who gathered outside the Baymak court when Alsynov was sentenced.

Authorities said the activist made racist remarks in a speech, but he says his comments have been mistranslated from the Bashkir language.

Bashkirs, a Turkic majority-Muslim people, account for around one-third of the region's four million residents.

Since sending troops into Ukraine, Moscow has escalated a decade-long crackdown on dissent, handing out lengthy prison sentences to critics.