MOSCOW (AP) — Alexei Navalny, Russia's most prominent opposition figure, has been detained by police and charged with unlawfully organizing a public gathering.

Navalny has called for demonstrators to protest on Saturday outside the mayor's office against the rejection of several opposition candidates from the ballot for this fall's Moscow city council elections.

In a short video on social media, Navalny said he was seized by police outside his home on Wednesday morning as he went out for a run and to buy flowers for his wife's birthday.

His lawyer Olga Mikhailova told the Interfax news agency that he had been charged with organizing an unauthorized gathering.

Conviction could carry a penalty of 30 days in jail and a fine of up to 300,000 rubles ($4600).