Riot police cleared protesters off the streets of Hamburg late on Tuesday, using water cannons, as tempers flared over whether protest camps will be allowed in the North Gerrman city during the G20 summit.

German security forces expect some 8,000 violent protesters to converge on the northern city of Hamburg this week where Chancellor Angela Merkel will host leaders of the G20 leading economies, Interior Minister Thomas de Maiziere said on Tuesday.

Police have so far banned the majority of camps for fear that extremist protesters might use them to prepare violent protests. In recent days, police have forcefully evacuated camps while protesters try and set up spontaneous ones elsewhere.

Some 20,000 police officers will secure the July 7-8 event in Germany's second-largest city where anti-capitalist protesters are expected to riot. Security circles say there could be up to 10,000 protesters prepared for violence.