A thousand "zombie" protesters have descended on Hamburg in protest against the two-day G20 summit between the "political elite" to be held in the northern German city on Friday.

The performance protesters dressed in grey from head to toe and, for several days ahead of the beginning of the summit, have been popping up in small groups across the city in silent, eerie protests.

Their performance piece culminated in a large gathering on Wednesday (local time), when organisers said about 1,000 volunteers walked slowly through the city.

About 1,000 volunteers took part in the performance protest. ( Reuters: Hannibal Hanschke )

The activist group, called Gestalten, said they wanted the G20 to stand for a more open, egalitarian society, rather than power in the hands of the few.

Organiser Sven Kammerer said the group wanted to send a symbol of solidarity and political participation out to the world.

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"The message of our performance is: No change can start from some political elite, it starts with you and me," Mr Kammerer told the ABC.

Similar forms of protests kicked off around the city, including a public rave in the harbour on Wednesday night. Several protests are planned throughout the summit.

Police disperse protests with water cannon

Hamburg boosted its police presence in the area with reinforcements from around the country and will have 20,000 officers on hand to patrol the city's streets, skies and waterways for the two-day summit.

Officials estimated about 8,000 protesters from Europe's violent left-wing scene would be in the city. Hamburg's police chief said known activists coming in from Scandinavia, Switzerland, Italy and elsewhere were being tracked.

Protests have kicked off around the city, with several planned throughout the summit. ( Reuters: Kai Pfaffenbach )

The atmosphere was tense in Hamburg on Monday night as police and anti-G20 protesters faced off in the city centre.

Thousands gathered in parts of the St Pauli neighbourhood amid a heavy police presence, occupying sidewalks and street corners with stalls and banners.

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In the early hours of Tuesday, police used a water cannon to try to disperse the crowds there.

Timelapse footage shows riot police forming a wall against protesters in Sternschanze neighbourhood in the city's north east on Wednesday.

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Protesters and police already had their first standoff on Sunday over a protest camp in Entenwerder, where protesters reported scuffles and the use of pepper spray against them.

Activists had erected a protest camp after a court ordered police to lift a ban on such camps.

Disputes arose, however, when police prohibited protesters from spending the night in the camp. The decision over the overnight use of the camp was referred back to the courts.