The Russian election committee has barred opposition leader Alexei Navalny from running for president in the 2018 presidential elections.
In a unanimous 12-0 ruling with one person abstaining, the committee cited a conviction for fraud as the reason Navalny could not take part as a presidential candidate.
Directly after Monday's decision, Navalny called for a boycott of the March elections.
"We are declaring a strike by voters. We will ask everyone to boycott these elections. We will not recognise the result," he said.
In a pre-recorded message, released shortly after the election committee made its ruling public, Navalny, 41, also criticised current president Vladimir Putin.
"Only Putin and the candidates he has handpicked are taking part in it.
"Going to the polls right now is to vote for lies and corruption," Navalny said in the recording.
Vladimir Putin, who has been in power since 1999, announced earlier this month he intends to run for another six-year term.
On Sunday, at a rally in front of about 750 supporters, Navalny called out Putin publicly.
"It's you, Vladimir Putin, who turned this country into a source of personal enrichment for yourself, your family and your friends. It's why you shouldn't be president any more, it's why you're a bad president," Navalny told the crowd that had gathered on a river bank on the outskirts of Moscow.
He started blogging about alleged corruption at some of Russia's large, state-controlled corporations, using social media to reach out to predominantly young followers.
Navalny was the driving force behind massive anti-Putin protests in 2011 and 2012, rallying tens of thousands of people across the country.
In 2013, he was first sentenced on embezzlement charges, after being accused of defrauding the Kirov regional budget of about $270,000.
The European Court of Human Rights last year quashed the ruling.
As a result, Russia's Supreme Court ordered a retrial.
Last February, in a retrial of the 2013 case, Kirov city court handed down a five-year suspended prison sentence and a fine of about $8,500 to Navalny.
Navalny has always maintained that the conviction was politically motivated.