MOSCOW — An activist from the punk collective Pussy Riot and two photographers have been detained during a protest outside the headquarters of the main Russian intelligence agency in Moscow.

Maria Alekhina’s associate Olga Borisova said Wednesday that she and Alekhina unfurled a placard saying “Happy birthday, butchers!” outside the building which used to house the KGB and is now home to the FSB agency. Borisova said she managed to escape but Alekhina and the photographers were detained.

Russia on Wednesday is marking the Day of Employees of State Security Agencies which coincides with the day when the predecessor of the KGB agency was set up 100 years ago, shortly before the Bolsheviks seized power.

Several hours after the detentions, Alekhina and one of the photographers remained in police custody.