The protesters gathered after the close of the summit in the Schanzen district, a stronghold for extreme left radicals which has been the site of multiple confrontations since Thursday.
Armed with glass bottles and targeting vehicles, many of which they set on fire, the protesters were pushed back by the police, using water cannon and tear gas, the police said on Twitter.
The police said more officers had been injured, and more people arrested.
On Thursday, a planned peaceful march by around 12,000 people protesting against globalisation turned violent.
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Friday's clashes occurred as leaders from the world's 20 biggest developed and emerging economies began the two-day meeting focusing on trade, terrorism, climate change and other key global issues.
Hamburg, a vibrant port city, is a citadel of leftwing radicals and authorities had long been bracing for possible violence on the sidelines of the summit.
World leaders made concessions on trade and climate language to US President Donald Trump Saturday at the end of the most fractious and riot-hit G20 summit ever, in exchange for preserving a fragile unity of the club of major industrialised and emerging economies.