STOCKHOLM, June 28 (Reuters) - Swedish clubs Hammarby and Djurgarden have been summoned to attend a crisis meeting after an explosive device was found outside Stockholm's new Tele2 arena, which the two sides are due to share. "According to our technicians, it was operational and not a dummy," police spokesman Sven-Olof Olsson told reporters. The device was found on Thursday as a Djurgarden masters team was preparing for a charity match, which rival Hammarby fans saw as an attempt to "claim" the arena by playing the first game there. ... More...