At least 76 people were injured in clashes with police on Thursday during the protest against the G20 summit, to be held here in Germany, the media reported.
The anti-globalisation "Welcome to Hell" rally peacefully but turned violent in the evening. The police had to use water cannon, pepper sprays and batons to disperse demonstrators, Xinhua news agency reported.
The "Welcome to Hell" rally is one the of a number of protests against both the G20 summit taking place in the city and US President Donald Trump's arrival, the Independent reported.
Police said beforehand they were expecting some 100,000 potentially violent activists from across Europe and beyond. As a result they had deployed more than 20,000 officers in the city.
The force they had repeatedly asked a group of anti-capitalist demonstrators to remove their masks and when they were ignored, they separated the group from the rest of the demonstration.
Black-hooded protesters attacked a police vehicle with bottles and bricks, breaking its window.
The violence broke out near the start of the demonstration at a riverside plaza used for Hamburg's weekly fish market.
The riots come amid mounting tensions about the conduct of local police some Hamburg residents have accused them of heavy-handed tactics.
Hamburg police said on its Twitter account that the number of protesters rose to 12,000 in the evening. Police called on all peaceful demonstrators to distance themselves from these violent protesters, Xinhua reported.
"Violent men equip themselves with scaffolds and stones. We are appalled at the obvious violence," the Hamburg police said. Damages of vehicles were reported at various areas of the city.
In various places in Hamburg, attacks on emergency personnel and property damage were reported, the Hamburg police said on twitter, adding a total of 15 policemen were injured and three of them must be treated in hospital.
The n-tv quoted Andreas Blechschmidt, a co-organiser of "Welcome to Hell" demonstration as saying that there were several injured demonstrators, including those injured by the use of police batons.