More than 300 inhabitants of Copenhagen's "free city" of Christiania, a giant squat, clashed with police late Tuesday putting up barricades and throwing petrol bombs after the police demolished an illegal building.
The demonstrators used guerrilla tactics, harassing the police in the streets around Christiania and setting fire to rubbish bins, chairs and old refrigerators.
Protesters said the police had provoked the action by demolishing a house that authorities said had been built illegally on a historic site, the old ramparts of Copenhagen.
As the enclave's main street Princessegade looked like a war zone with blazing barricades and clouds of tear gas, Copenhagen police spokesman Flemming Steen Munch said at least three demonstrators had been arrested. It was not known if people had been hurt in the confrontations.
An alternative community founded by hippies in 1971 in an abandoned military barracks near the centre of the Danish capital, Christiania is home to some 1,000 hippies, artists, activists and misfits as well as to restaurants, cafes, shops and some unique-looking homes designed by residents.
Politicians have been divided over the community, with some seeing it as an interesting social experiment, while others say it is merely a den of drugs and crime.
A popular tourist attraction, the area also has the dubious reputation of being the biggest drug market in Scandinavia. But police crackdowns since March 2004 have nearly wiped out the drug trade.
