A top associate of Russian opposition leader Alexei Navalny has been sentenced to 20 days in jail in connection with an unsanctioned protest rally last year.

Leonid Volkov was sentenced late Wednesday on charges of violating the rules for holding a rally.

Navalny is an anti-corruption campaigner and the most prominent foe of Russian President Vladimir Putin. Volkov, who is Navalny's chief of staff, helped organize a rally last September to protest the government's decision to raise the pension age.

The rally drew several thousand protesters in a challenge to the Kremlin.

Navalny and Volkov have served numerous stints in jail for organizing unsanctioned protests.