German police have said they are bracing themselves for violent protests in the capital on 1 May, a traditional day for leftwing demonstrations.

As many as 20,000 activists are expected to concentrate their protests on the eastern district of Friedrichshain, railing against the spread of gentrification in the part of Berlin where the majority of new property developments are taking place.

For decades, the International Workers’ Day protests have focused on the southern district of Kreuzberg, with hundreds of demonstrators typically clashing with riot police, using stones and molotov cocktails when darkness falls.

But in recent years, there have been increasing attempts to highlight the situation in districts previously behind the iron curtain, which have undergone the most radical changes over the past three decades.

A particular focus will be Friedrichshain’s Rigaer Straße, until recently home to some of the last squats in Berlin.

Four years ago, the area around Rigaer Straße was declared a danger zone. Since then, police who monitor the district in vehicles on a daily basis have had permission to carry out stops and searches.

Residents have complained they have often only been allowed home after being accompanied to their front doors by police officers suspicious of their movements, who check their keys fit in the door.

The squats were cleared to make way for property developers, as well as a nearby building project of luxury flats called Carré Sama-Riga, which has become a particular thorn in the side of those protesting against the squeeze on affordable housing in the city, as long-term residents are forced out by property investors.

Rents in Berlin are said to be rising higher than almost anywhere in Germany.

Protesters, led by the “1 May Revolutionaries”, who for weeks have been calling on people to demonstrate under the slogan “against the city of the rich”, say they are trying to highlight a question central to many Berliners: to whom does their city really belong?

About 15 separate demonstrations have been planned across the city. Police have said they will pay particular attention to a lunchtime protest due to be held in the villa district of Grunewald, where protesters wish to highlight the influence of property speculators. Described by organisers as a satirical event, demonstrators will also seek to enter dialogues “over the garden fence” with residents.

A total of 5,500 police officers are expected to be on duty, with reinforcements having been sent from four other German states. About 900 officers are being placed in Grunewald.

Despite the shift of the focus from Kreuzberg, 1,600 officers are expected to be on the streets in the district, where two main thoroughfares have been closed to traffic as locals celebrate a street festival. Police said they also had to take into account the danger of terror attacks. Roads and bridges have been blockaded with huge synthetic cubes filled with water.

As much as the protests draw political demonstrators, during the day, the street party atmosphere is a huge attraction for residents and tourists.