The four existing mosques in Russia’s largest city are overcrowded during the Muslim holidays. But Mayor Sergei Sobyanin declared this week that new ones will not be built because they are used by migrant workers, according to the Christian Science Monitor. He claimed that between 60 and 70 percent of Muslim worshipers are migrants.

One new mosque is currently under construction. But there won’t be any more, the mayor said.

"No new building permits will be issued. I think that's enough mosques for Moscow,” Sobyanin told Russian daily newspaper Komsomolskaya Pravda.

There’s already hostility toward Muslims in Moscow, and the mayor’s decision is sure to inflame tensions. It’s true that many Muslims worshipping in Moscow are migrant workers—there are 2 million of them, according to travel magazine Roads & Kingdoms.