Authorities in the Siberian city of Omsk banned a so-called Zombie Parade that was to be held on Saturday in support of Russia’s punk band Pussy Riot, Ekho Moskvy reported on Thursday.

Mikhail Yakovlev, one of the parade’s organizers, said there was no official explanation from the authorities, but he believes it was banned because of a series of letters from Orthodox and Muslim organizations, as well as from public groups.

“Unofficially I was shown letters sent to the mayor and the governor from the Taurida Diocese of Omsk, the Union of Omsk Muslims, the Committee of the Territorial Public Self-Administration, as well as from the Parental Control organization,” Yakovlev said in an interview with Ekho Moskvy radio.

The activist said the request for permission to hold the parade was submitted to the municipal authorities a month ago and they pledged to coordinate all the details for the event to go ahead on August 19. But on Thursday the authorities issued a denial.

The organizers, who have been seeking to hold the parade for several years now, said earlier that they wanted to dedicate this year’s event to members of the Pussy Riot band, who remain jailed over their irreverent “punk prayer” in Moscow’s Christ the Savior Cathedral in February.

The Pussy Riot case has split Russian society, with some rooting for harsh punishment and others saying a prison sentence would be excessive.