Protesters behind police fences shout slogans during an outlawed May Day rally in central Istanbul May 1, 2009. Turkish riot police fired water cannon and tear gas in clashes with May Day demonstrators in Istanbul on Friday. Thousands of police regulated access to the city's main Taksim square, which has been closed to workers' demonstrations since 37 people died in a shooting by an unknown gunman or were trampled to death on May Day in 1977. REUTERS/Umit Bektas (TURKEY POLITICS CONFLICT)