Thousands of anti-globalisation protesters have gathered in northern Germany to demonstrate outside the G8 summit.
Some 16,000 officers have been deployed near the seaside resort of Heiligendamm, where the leaders of the eight top industrialised nations are meeting.
For a short time on Wednesday protesters cut off all ground access to the summit.
Several police were hurt as officers fired water cannon at stone-throwing demonstrators.
Anti-globalisation groups called off the main protest planned for Thursday after it was banned.
Two boats operated by Greenpeace were intercepted as they broke through a Baltic Sea cordon to try to deliver a message to G8 leaders.
The protesters - some of whom came dressed as clowns - are staging their own parallel meeting close to the summit venue.
US President George W Bush is one of the main targets of the demonstrators' anger.