Russia's highest court has upheld election officials' decision to bar opposition leader Alexei Navalny from running for president in March's election.

The Supreme Court on Saturday turned down Mr Navalny's appeal against the Central Election Commission's move, saying that the decision to bar him from the race fully conforms with the law.

President Vladimir Putin, whose approval ratings top 80%, is set to easily win a fourth term in the March 18 vote.

Mr Navalny has campaigned for the presidency all year despite an implicit ban on his candidacy due to a fraud conviction seen by many as politically driven. Election officials formally barred him from the ballot last Monday.

Mr Navalny responded to the ban by calling for a boycott of the vote. The Kremlin said authorities would look into whether such a call violates the law.

Mr Navalny responded to Saturday's court ruling by repeating his call for a "voters' strike".

"We don't acknowledge elections without competition," he said on Twitter.

Many others have declared their intention to run. They include veterans of the past campaign - ultranationalist Vladimir Zhirinovsky and liberal Grigory Yavlinsky - as well as communist nominee Pavel Grudinin and star TV host Ksenia Sobchak.

While none of them poses a serious challenge to Mr Putin, the Kremlin is worried about voter apathy and has focused on boosting turnout to make his victory as impressive as possible.

The involvement of Ms Sobchak, the daughter of the late mayor of St Petersburg who was Mr Putin's boss in the 1990s, could raise public interest in the race.

While the 36-year-old has denied colluding with the Kremlin, her participation could draw some of Mr Navalny's supporters to her side and help improve turnout.