Protesters focused on the eastern district of Friedrichshain, which has followed others in becoming a target for property developments many people complain are squeezing them out of the housing market.

Protest organisers said they stopped counting the number of demonstrators at 10,000.

A total of 5500 police officers were on duty for the day. They detained some protesters but a police spokesman could not immediately say exactly how many.

"People on low and middle incomes can't afford to rent a new home any more," complained local resident Wolfgang Hardt.

Demonstrators chanted "the streets are ours" and "anti-capitalism". Some, dressed in black and wearing masks, lit flares from apartment balconies.

For decades after unification in 1990, Berlin became a magnet for artists, musicians and students drawn by housing far cheaper than in other major European cities.

Around 85 per cent of Berliners rent their homes rather than own them.

But with an influx of 40,000 people a year in the past decade, rents have more than doubled since 2008, according to a study by online housing portal immowelt.de.

The city is no longer a bargain for newcomers and many of its longer-term residents say they are struggling.

Among the properties sold off to the private sector are many of the large landmark Communist-era housing projects built as showpieces under the former East Germany.

Many have been acquired in recent years by Deutsche Wohnen, the city's largest landlord with around 115,000 flats.

Last month, thousands of Berlin residents took to the streets to vent anger over surging rents and demand the expropriation of more than 200,000 apartments sold off to big private landlords, which they blame for changing the character of the city.

Australian Associated Press