Turkish police on Tuesday sealed off Istanbul’s central Taksim Square to prevent any May Day protests as President Recep Tayyip Erdogan warned unions to stay away from any provocative steps. High metal barriers were erected around the square, AFP journalists reported. The stepped-up security measures came a day after Interior Minister Ali Yerlikaya said authorities had designated 40 areas for May Day celebrations with the exception of the emblematic Taksim Square. Yerlikaya said some unions had demanded to use the square, the epicentre of 2013 protests against the government of then prime mini…