Friday night's violence in Hamburg was centred around the city's Schanzenviertel neighborhood, where according to police some 150 left-wing demonstrators lit a bonfire in a street outside a youth centre, threw bottles and stones at police, and damaged a bank branch.
At least 14 people were injured in the clashes, including a passer-by who was taken to hospital after being hit on the head by a flying rock. In addition, thirteen police officers and three police dogs sustained injuries. Seven rioters were arrested.
Hamburg's Schanzenviertel neighborhood has been the scene of similar May Day clashes in recent years.
In Berlin, however, the night passed comparatively uneventfully, despite fears that the levels of May Day violence could be high this year. Berlin police reported that the around 4,000 people celebrating Walpurgis Night in the streets of the German capital did so relatively peacefully.
At Berlin's Boxhagener Platz in the Friedrichshain neighborhood, a few bottles and beer cans were thrown at police, but the large contingent of officers on the scene kept the situation under control. Several inebriated people were arrested but no injuries were reported.
The situation thus far has been markedly calmer than in 2009, when violence on the May Day weekend returned to the capital with a vengeance. Last year some 500 officers were injured and just under 300 people arrested.
For May Day itself, Saturday, police have prepared several large-scale operations aimed at heading off possible violence. A march by around 3,000 neo-Nazis is planned while some 10,000 left-wing anarchists are expected to gather in Berlin's Kreuzberg, an ethnically diverse, left-leaning neighborhood.
Police will try to keep the two demonstrations separate and are deploying 6,000 officers in the streets. Police reinforcements from other federal states have been sent to the capital.