City Hall on Wednesday banned a rally in support of jailed opposition activist Sergei Udaltsov and other political prisoners, for which about 2,000 people signed up on Facebook.

Organizers reported earlier this week obtaining a sanction to rally on Pushkin Square on Thursday, but Udaltsov's wife Anastasia said on her blog that the Moscow government refused a permit. No explanation was provided.

By contrast, St. Petersburg authorities allowed a rally on Friday, the event's Facebook group said.

Anastasia Udaltsova urged the protesters to still take to the streets, either without any slogans and banners, which would mean that the gathering does not qualify for a rally, or in a line of one-person pickets, which requires no special sanction.

Radical activist Udaltsov was detained on the eve of parliamentary elections on Dec. 4 and kept behind bars under short-term arrests ever since. He staged several hunger strikes in detention.

Udaltsov's release was among the demands of last week's rally on Prospekt Akademika Sakharova, the biggest in Moscow since 1993.