Police searched the St. Petersburg headquarters of opposition leader Alexei Navalny Tuesday evening and detained his campaign’s coordinator, the St. Petersburg news site Fontanka reported.

Navalny has announced he will run for president next March despite a criminal conviction, which he says is politically motivated, barring him participating. He was jailed for 20 days on Oct. 2 for calling for organizing unauthorized campaign events.

Andrei Pivovarov, an activist at the Open Russia movement founded by exiled tycoon Mikhail Khodorkovsky, said the police were looking for leaflets advertising an unauthorized rally on Oct. 7, President Vladimir Putin’s birthday.

Polina Kostylyova, the coordinator of Navalny’s campaign headquarters in St. Petersburg, was detained by police during the search, a lawyer who works with Navalny’s Anti-Corruption Fund said on Twitter.