Moscow (CNN) Russian opposition activist Alexei Navalny was briefly detained in Moscow on Thursday, ahead of the country's presidential election from which he has been banned.

Navalny, the best-known political opponent of President Vladimir Putin, reported his detention in a series of tweets and said authorities had begun legal proceedings against him for organizing anti-government protests.

It's not clear when he might face court, but he could be jailed for a maximum of 30 days and could possibly still be in prison for the March 18 election.

His chief of staff, Leonid Volkov, tweeted that he, too, had been detained.

The Kremlin appears to have made efforts to stifle the main opposition before the vote and Putin is expected to win by a landslide. Navalny is calling on Russians to boycott the election to strip Putin of his legitimacy.

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