Russian news agencies say a Moscow court has sentenced opposition activist Aleksei Navalny to 30 days in jail after convicting him of violating protest laws.
The August 27 ruling by the Tverskoi District Court effectively bars Navalny from participating in a protest next month targeting a controversial government proposal to raise the country's pension age.
The court found Navalny guilty of breaking protest laws by helping to organize a street rally in Moscow in January despite authorities' refusal to sanction it.
That demonstration in Moscow, along with similar protests in other Russian cities, drew thousands of people opposed to the reelection of President Vladimir Putin.
Navalny’s lawyers said they will appeal the ruling.
Navalny, who was arrested outside his home on August 25, has said that his latest case represents an attempt by the authorities to disrupt rallies across Russia planned for September 9 against the pension proposal.
A vocal foe of Putin, Navalny has organized large street protests on several occasions and published a series of reports alleging corruption in Russia's ruling elite.
He was barred from the March presidential race due to a conviction on financial-crimes charges he contends were fabricated by the Kremlin to sideline him from the March 18 vote.
Putin overwhelmingly won the election, garnering almost 77 percent of the vote -- more than he received in any of his three previous elections and the highest percentage handed to any post-Soviet Russian leader.
The government's proposal to raise the retirement age has stoked widespread anger across the country and has undermined Putin’s popularity.
The Russian parliament has given preliminary backing to the proposal that would raise the retirement age to 63 for women by 2034 and to 65 for men by 2028. Currently, the retirement age is 55 for women and 60 for men.
The plan sparked widespread anger after it was announced in June, and Putin's approval ratings have fallen.