Mon May 1, 1:57 PM ET

BERLIN (AFP) - Neo-Nazis and some 10,000 left-wing protestors clashed violently in Germany, with the two sides pelting each other with stones and bottles in the eastern city of Leipzig, police said. ADVERTISEMENT

The trouble began when 5,000 people tried to stop protest marches by about 550 neo-Nazis in the city by blocking the streets with burning trash cans, police said.

About 2,000 police officers who had been brought in from around the country eventually separated the two groups, arresting 20 people.

In the northeastern city of Rostock some 500 members of Germany’s extreme right National Democratic Party clashed with about 4,000 counter-protestors, police said, adding that they arrested 40 people there.

In Heppenheim, in the central state of Hesse, police managed to keep apart some 400 right-wing extremists and 700 counter-protestors.

Police said in Hameln, in Lower Saxony state, swastikas and other banned symbols were painted on buildings and parking spaces on Monday.

The co-president of the Greens, Glaudia Roth, called for stronger laws against right-wing extremist groups and said Germans should not believe that support for neo-Nazis was limited to the poorer former East Germany.

"Those who try to portray this as a problem of the east forget that the leaders of these groups come from the west," she said.

In Germany neo-Nazi demonstrations often provoke much larger counter protests and end in clashes with the police, particularly on May Day.

In Berlin’s Kreuzberg district, which is home to a large Turkish community, several hundred people marched through the streets in support of Kurdish and Maoist organisations on Monday.

Police said they had deployed some 5,500 offices in Kreuzberg because they were expecting left-wing groups to launch protests here later in the day.

The area is known for unrest during Walpurgis Night, May Day’s Eve celebrations, which have their roots in a pagan spring rite.

But police chief Dieter Glietsch said Sunday night was one of the quietest Walpurgis celebrations in years.