The explosion took place when worshippers had gathered in the mosque for the afternoon prayers.A heavy contingent of police has rushed to the spot to cordon it off.The explosion was powerful enough to shatter window panes of nearby buildings and the blast was heard for areas relatively far away as well.Rescue workers and ambulances have rushed to the spot. They said they have shifted at least 20 people thus far to the nearby the Lady Reading Hospital and the Khyber Teaching Hospital.The area is located in a highly secure area of Peshawar with Police Secretariat and PTCL Colony all located nearby.To access the area, people have to cross several police check posts. With no commercial area located within the police lines, only people with authorized access can enter the area.