Several hundred anarchists, who call themselves "Black Bloc", have been holding "Welcome To Hell" protests since Thursday, to disrupt the G20 summit attended by world leaders including U.S. President Donald Trump.
Protests turned violent on Friday at the popular Schanzenviertel district of the city, as several masked demonstrators set several cars on fire, and threw rocks and bottles at police officers.
Hamburg police responded with tear gas and water cannons.
Amid escalating tensions, a police officer fired a warning shot, police said on Twitter.
At least 196 police officers have been injured during the ongoing riots while more than 50 protesters have been arrested.
The Black Bloc group blamed the police for the escalating tensions and for using disproportionate measures.