Alexei Navalny, Russia's most prominent opposition figure, has been released from jail after a 20-day sentence for calling an unauthorized demonstration.

Navalny was arrested on Sept. 29 as he planned to travel to the city of Nizhny Novgorod for a rally that had been given official permission. But a court sentenced him for calling another rally, an unauthorized protest in St. Petersburg, President Vladimir Putin's hometown.

Navalny, who plans to run for president against Putin in next March's election, has repeatedly served jail terms connected to rallies. After his release Sunday, Navalny said on social media that he hopes to attend an evening demonstration in the southern city of Astrakhan.

The anti-corruption campaigner this year twice called for demonstrations nationwide whose size and extent rattled the Kremlin.