Russian migration officials disrupted a Moscow play by a Swiss director about the trial against punk band Pussy Riot on Sunday, while religious activists caused a commotion outside. The political play \"The Moscow Trials\" by director Milo Rau tells the story of last year\'s trial against three singers of the feminist band -- one of whom, Yekaterina Samutsevich, has since been freed and is now taking part in the play. Russia\'s migration service confirmed that its employees entered the Sakharov Centre, a human rights museum staging the performance, and asked Rau to show his work documents in the middle of the play. \"Mr. Rau was warned about the necessity to follow migration regulations,\" deputy head of the service Sergey Kalyuzhny told RIA Novosti news agency. The director\'s business visa does not allow \"work activity\", he said. Perplexed employees of the Sakharov Centre said at first that they were not sure whether the visitors were migration officials or Orthodox activists in fake uniforms. \"It was an attempt to disrupt the play, and they succeeded for two hours,\" said Yelena Kaluzhskaya, the spokeswoman of the Sakharov Centre, adding that the officers had a television crew with them. \"I don\'t doubt that they targeted the Pussy Riot play,\" she said. The visitors, wearing purple vests emblazoned with the words \"Immigration Control\" asked the play\'s creator for his visa documents and questioned the director of the Sakharov Centre in his office, Kaluzhskaya told AFP. Nobody was detained. The play was later interrupted again because of Orthodox activists and Cossacks outside the venue. Police units were called in, and organisers invited five Cossacks to watch the performance to show it was not anti-religious, another employee Mikhail Kaluzhsky wrote on Facebook. \"Sakharov Centre is surrounded by people in Cossack uniform and police which seems to be keeping order,\" Kaluzhsky said. An AFP correspondent also observed a truck with special forces units parked near the building. Members of Pussy Riot entered the Cathedral of Christ the Saviour last February to stage a short performance in bright-coloured dresses and balaclavas protesting against the increased involvement of the Russian Orthodox Church in politics and Vladimir Putin\'s presidential campaign. They were controversially sentenced to two years in jail on hooliganism charges in a closely-watched trial that was slammed by the West and divided Russian society. Yekaterina Samutsevich was released in October but two other band members are serving their sentences in distant penal colonies. Orthodox activists and Cossacks have disrupted several Pussy Riot-related events in the past, including plays and rallies in support of the women.