Moscow ( CNN ) -- Police detained about 40 gay-rights activists in Moscow on Sunday , alleging they attempted to hold an unauthorized demonstration during Moscow gay pride events , the police press service said . State-run Russian news agency RIA Novosti reported that prominent gay rights activist Nikolai Alexeyev and several others were among those detained during an authorized picket near Moscow 's city hall . `` The picket was devoted to the anniversary of the decriminalization of homosexuality in Russia and was not sanctioned by the authorities , '' RIA Novosti said . Activists have held similar gay pride demonstrations in previous years , but usually disperse before police arrive , according to the news agency . Incumbent Moscow Mayor Sergei Sobyanin and his predecessor , Yury Luzhkov , have both spoken against public gay-rights rallies , with Luzhkov calling them `` Satanic , '' according to RIA Novosti . An authorized gay pride rally took place in St. Petersburg for the first time May 17 , the news agency said , but `` dozens of unidentified thugs attacked the activists after the event , beating them up . '' One activist was detained , but RIA Novosti said there were no serious injuries or damages from the incident . CNN 's Arkady Irshenko contributed to this report .
Police say the activists were holding an unauthorized demonstration . Report : A prominent activist was among those detained . The incident took place outside the Moscow city hall , reports say .