New Delhi, Aug 31 : The Delhi Police's Special Cell has detained two men from Punjab over charges for defacing walls at five Delhi Metro stations with pro-Khalistani messages, officials said on Thursday. A video purportedly released by the banned organisation Sikhs for Justice (SFJ) displayed the vandalised metro station walls. In the video, Gurpatwant Singh Pannun, spokesperson for SFJ, said: "During the G20 Summit in Delhi on September 10, we will be orchestrating a Khalistan referendum in Canada." A senior police official said that the apprehended individual is currently being interrogated. Previously, the police had reported that unidentified individuals had vandalised the walls of the Shivaji Park, Madipur, Paschim Vihar, Udyog Nagar, and Maharaja Surajmal Stadium metro stations with the slogans "Delhi Banega Khalistan" and "Khalistan Zindabad". A government school wall in Nangloi had also been defaced. This G20 Summit in Delhi will take place on September 9-10. /IANS