(Reuters) – Police on Sunday detained three further suspects in an alleged Islamist plot to attack Germany’s famed Cologne Cathedral on New Year’s Eve, authorities said. The alleged attackers had planned to use a car to attack the 800-year-old Gothic edifice by the Rhine river, Cologne police director Frank Wissbaum told a news conference. The method of the planned attack was unclear, but an underground car park below the cathedral had been searched with explosives sniffer dogs overnight, he told reporters. “The three people are now securely in custody, which we are very glad about since they …