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By Tom Armitage

ROSTOCK, Germany, June 2 (Reuters) - German police clashed with hundreds of protesters in the port of Rostock on Saturday following a much larger peaceful demonstration against next week's Group of Eight summit in a nearby Baltic resort.

About 2,000 protesters, identified by police as a hard core of violent activists, threw bottles, sticks and stones at riot police, on the fringes of a rally in the town's harbour area.

The protesters, most of whom were clad in black from head to toe, set fire to a car, damaged shop windows and torched bins.

Tens of thousands had earlier taken part in two peaceful marches protesting against the G8 which converged at the harbour where rock music and speeches were planned.

"The so-called 'black block' of activists were agitating," police spokesman Ingolf Dinse said. "They attacked a car and then attacked police massively, they threw stones and rockets at police, prompting us to change our plans and respond."

Water cannons and tear gas were used to disperse the violent protesters, who had gathered around the edge of the rally and in the narrow streets of the restored, medieval harbour town.

Dinse said that by 1900 GMT the majority of the protesters had dispersed and police had restored order.

Around 150 police officers were wounded in the violence, some 25 seriously, and about 50 people were arrested, police said. There were no details on wounded protesters.

Earlier, a diverse group of peaceful marchers passed through an overcast Rostock, blowing whistles and waving banners with slogans ranging from "Stop Privatisation!", to "World Peace Now!" and "Water Is A Human Right!".

Church groups, feminist organisations and German labour unions all took part. One group came dressed as medieval kings.

"We are trying to show the similarities between the kings of the dark ages and how the Group of Eight behave today," said Sigurd Jakobsen, a Danish student dressed a British monarch.

Up to 100,000 people had been expected but police said only 25,000 people attended. Organisers disputed the police figures and said at least 80,000 people had turned up.

TIGHTER SECURITY

Many wore face masks of U.S. President George W. Bush and Russian President Vladimir Putin. Both will join German Chancellor Angela Merkel and other G8 leaders in the resort of Heiligendamm next week for their annual summit meeting.

In recent years, security surrounding the G8 has been stepped up after riots and the death of a protester at the 2001 summit in Genoa. Some 16,000 German police are on duty for the summit, the biggest force in post-war German history.

During the summit itself, which will take place on June 6-8, protesters will be prevented from approaching the exclusive hotel venue. A 12-km security fence has been built around the Baltic resort and access is tightly controlled.

The measures have been described as heavy-handed by some left-wing groups. Last month police raided left-wing premises, prompting street riots in Berlin and Hamburg.

Demonstration organiser, Werner Raetz, warned earlier that stringent police checks could anger protesters.

"What we do fear is the police's actions in the next few days could anger people to the extent that they do things which are not planned," he said before the demonstration.

Germany's right-wing National Democrats are also protesting against the G8. Police arrested about 13 people in Berlin and about 150 more in Schwerin after an NPD rally was banned. (Additional reporting by Sabine Siebold and Madeline Chambers in Berlin)

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