MOSCOW — Russian election officials on Monday formally barred Russian opposition leader Alexei Navalny from running for president, prompting calls from him for a boycott of next year’s vote.

The Central Election Commission decided unanimously that the anticorruption crusader is not eligible to run.

Navalny is implicitly barred from running for office because of a conviction in a fraud case that has been viewed as political retribution. He could have run had he been given a special dispensation or had his conviction been vacated.

President Vladimir Putin is set to easily win a fourth term in office in the March 18 election, with his approval ratings topping 80 percent.

Over the past year, Navalny has mounted a grass-roots campaign, reaching out to the country’s remote corners.

Navalny, 41, is the most serious challenger that Putin has faced in all his years in power, and the court cases against him have been widely seen as a tool to keep him from running for office.

In a prerecorded video message released minutes after the Election Commission handed down the decision, Navalny called on his supporters to boycott the vote.

‘‘The procedure that we’re invited to take part is not an election,’’ he said. ‘‘Only Putin and the candidates he has handpicked are taking part in it. Going to the polls now is to vote for lies and corruption.’’

Central Election Commission chief Ella Pamfilova told Navalny ahead of the vote to bar him that ‘‘maybe we would be interested if you were running,’’ but said the conviction doesn’t allow the commission to put him on the ballot.

Speaking before the vote, Navalny told the commissioners that their decision to bar him would be a vote ‘‘not against me but against 16,000 people who have nominated me, against 200,000 volunteers who have been canvassing for me.’’

ASSOCIATED PRESS