Anti-capitalist protesters faced off against police across central Hamburg into the early morning hours of Saturday.
Elsewhere in the city, leaders of the world’s 20 most powerful countries were attending the two-day summit.
Police deployed water cannons and called in reinforcements from around Germany to help battle escalating street violence.
People began looting supermarkets and other businesses and torching vehicles on the streets.
An ATM machine was burned, and several police helicopters patrolled overhead.
Police earlier said at least 196 officers were injured in the clashes.
Authorities detained 83 protesters temporarily at the scene and 19 were taken into custody.