Cars appear to have been targeted at random
Street battles lasting several hours have gripped the German port city of Hamburg, in what police describe as the worst riots there for years.
Left-wing demonstrators angered by a neo-Nazi rally hurled bottles at police and set cars and rubbish bins ablaze. Police responded with water cannon.
The violence erupted on Thursday evening, after thousands of protesters had gathered in the city for May Day.
About 250 rioters were detained and about 20 police officers reported hurt.
Police said about 7,000 leftists tried to break through a police cordon shielding about 1,100 far-right demonstrators.
Police use water cannon to disperse rioters on the streets of Hamburg
The violence centred on the Barmbek district of Hamburg.
The neo-Nazis had travelled to Hamburg from all over Germany. Some of their buses were damaged in the violence.
Leftists set several cars ablaze and erected street barricades with planks, street signs and rubbish, local officials said. A police vehicle was among those set on fire.
Some of the neo-Nazis also got involved in fights. Germany's Der Spiegel website says several journalists were assaulted by them.
Lower-level violence also erupted at May Day demonstrations in Berlin and Nuremberg on Thursday.