Russia temporarily freed Alexei Navalny on Friday, bending to the will of protesters who denounced the opposition leader's five-year jail sentence as a crude attempt by President Vladimir Putin to silence him.

People took to the streets of Russia's main cities in their thousands on Thursday to vent their anger after a court in the city of Kirov convicted Navalny of what he says were trumped-up theft charges. More than 200 were detained.

In a move that could be designed to head off more unrest, the court accepted an unusual request by prosecutors to let Navalny out of detention to await the outcome of an appeal, but said his movement would be restricted.

"I am very grateful to all the people who supported us, all the people who went to (protest on Moscow's) Manezh Square and other squares," Navalny, 37, said after he was released from a glass courtroom cage and embraced his wife.

Navalny, an anti-corruption campaigner who has led protests against Putin, was convicted on Thursday of organising a scheme to steal at least 16 million roubles ($494,000) from a timber firm when he was advising the Kirov regional governor in 2009.

He says he did nothing wrong and that the sentence is intended by Putin to sideline him as a potential political rival. The United States and the European Union criticised the verdict and said it raised questions about the rule of law.