Navalny, who has said he will run for president next March, received a 300,000 ruble ($5,000) fine, with his two supporters given lesser penalties.

The three men were found guilty of violating rules on the organisation of public events by calling on Navalny's supporters to take to the streets on July 8-9 to distribute leaflets to people in Russian towns.

Dozens of supporters of Navalny, the Kremlin's foremost critic, were arrested by police over the two days.

Last month, Navalny himself walked free from jail after serving 25 days for having organised unauthorised protests against President Vladimir Putin's rule.

Russia's electoral authorities said in June that Navalny's five-year suspended sentence for embezzlement means he is ineligible to run.

Navalny insists that the conviction was politically motivated.