Berlin - A street party in Hamburg turned violent overnight after leftist demonstrators went on the rampage, police in the northern German port said Sunday.

Eighteen people were injured, 11 of them police officers, following the event in the Scheunenviertel area of the city, renowned for the many residents adopting an alternative, anti-authority lifestyle.

Police deployed water cannon and used riot sticks to break up the gathering. Some 950 officers were on duty to contain the violence.

Police detained 39 people temporarily after the demonstrators erected street barricades, set fire to refuse containers and broke shop windows. They also pelted passing cars with stones.

The fire brigade doused 13 small fires.

A street party in the area turned violent last year. The protests are similar to the May Day clashes with police that have taken place virtually every year for the past 20 years in Berlin's Kreuzberg-Friedrichshain area.

On Saturday several thousand people protested largely peacefully against the German extreme rightwing in various centres.

In the Bavarian town of Memmingen, hundreds turned out to protest against a meeting by around 120 members of the German National Party (NPD) in the local town hall.

In Dortmund, some 3,000 protestors turned out to counter a rally of about 1,000 right-wingers.

In Magdeburg, 200 people participated in a commemoration for a 20-year-old art student who was murdered three weeks ago by suspected right-wingers. (dp)