May Day violence is so far down compared with previous years, but further protests in cities around Europe are expected later in the day.
May Day is expected to see violent protests in a number of European cities
Dozens of police were injured in Berlin and Hamburg in the early hours of the May Day holiday as protestors clashed with police.
However, the authorities have said that the violence was more subdued than on previous May Day bank holidays.
Police in Berlin said that 48 riot police were hurt and 49 people arrested when around 200 protestors chanting anti-capitalist slogans threw bottles and stones at police after a street party in the eastern district of Friedrichshain.
Several dumpsters were set on fire as the otherwise peaceful gathering of about 2,000 people was ending, police said. Demonstrators also threw bottles and stones at trams and cars. Several glass windows at bus stops were destroyed.
In Hamburg, authorities said three riot police were injured in clashes with demonstrators.
Police in Berlin are bracing for further violence on Friday when members of far-right parties, labor unions and leftists march. The economic crisis, which has sent unemployment soaring and raised public ire over a growing disparity in wages, along with simmering anger over "gentrification" in some low-rent districts have raised police worries about this year's May Day.
Germany's capital has been rocked by violent clashes between police and groups of anti-capitalist and anarchists on May Day for years.
Since the clashes started in 1987 they have caused extensive damage to parts of the city. But the violence had been on the wane in the last three years after police shifted tactics from battling rioters to de-escalation.
May Day is traditionally marked by union rallies in many European countries and the global economic downturn is expected to swell the crowds this year. Germany is suffering its worst recession since World War Two.
In France, the eight main unions have called for massive nationwide protests against President Nicolas Sarkozy's handling of the economy and a big union demonstration is also expected in Madrid, Spain.
Meanwhile in Istanbul, Turkish police sprayed tear gas and used water cannons to prevent hundreds of leftist protestors from marching to an Istanbul square to mark May Day in defiance of a ban.