Six terrorists entered an army-run school in Peshawar in Pakistan on Tuesday morning and opened fire, killing at least 18, including 16 children.The terrorists, dressed in army uniforms, entered the school through a graveyard near the back entrance and started firing, say witnesses. ( Read more for updates At least 500 children and teachers were in the school at the time. The gunmen allegedly went from room to room, barking orders at children. They had orders to shoot "older students, not children," Taliban spokesperson Muhammad Khorasani was quoted as saying by Agence France-Presse."It was the fourth period and we heard firing," said one child who was let out of the school."We were asked to sit in the auditorium until the firing is over," he said.Another older student said, "We were asked to lie down on the floor. We did that for an hour as firing went on. We were let out through the exit."Worried parents and security forces gathered at the spot as firing took place between the terrorists and the army.

Heavy gunfire could be heard from inside the school as soldiers surrounded it. According to an official tweet, artillery, helicopters, military, police, intelligence and ground forces are in the area to stop the terrorists.Pakistan Prime Minister Nawaz Sharif has condemned the attack, which is being linked to the Pakistani army's offensive against terrorists in North Waziristan near the Afghan border.