German police have clashed with hundreds of anti-globalisation demonstrators in the northern city of Hamburg, arresting 21 people.

Police used water cannon and baton charges against protesters, who pelted them with bottles and stones.

The violence followed a march by about 4,000 activists angered by what they saw as excessive security for a meeting of EU and Asian foreign ministers.

Germany is also tightening security ahead of next week’s G8 summit.

A fence has been erected around the German Baltic Sea resort of Heiligendamm, where the summit will take place on 6-8 June. Protests will be banned from the area of the barrier.