Demonstrators (L) clash with riot police as they try to march during an anti-G20 protest in downtown Seoul November 11, 2010. World leaders are gathering in Seoul on Thursday and Friday for the Group of 20 summit aimed at safeguarding the global economic recovery and defusing trade and currency tensions. REUTERS/Jo Yong-Hak (SOUTH KOREA - Tags: CIVIL UNREST POLITICS BUSINESS IMAGES OF THE DAY)