Zurich police used rubber bullets and tear gas to disperse an illegal rave in the early hours of Sunday, in their third clash with party-goers in eight days.
Police chief Philipp Hotzenköcherle said at a media conference on Sunday afternoon they had arrested 91 people, of whom 48 remained in detention.
A total of 62 face charges, mainly for breaches of the peace, but also for violating the law forbidding people to hide their faces and for violence against the police.
Only six of those detained were aged over 25, and two thirds came from outside the city of Zurich. The head of the police department, Daniel Leupi, described them as “riot tourists” and said they had come simply for the sake of violence.
The trouble started when police moved to break up the illegal party late on Saturday evening in the area around Zurich’s central railway station.
Small groups then threw stones, damaged shop windows and cars, and set fire to rubbish bins.
They caused damage worth between SFr100,000 ($114,000) and SFr200,000 and the cost of the police intervention amounted to about SFr200,000. One female police officer and another woman were slightly injured, according to Hotzenköcherle.
Police had already clashed with illegal party goers in the early hours of Saturday morning although on that occasion no damage was reported.
Last weekend eight policemen were hurt when a number of people attending another illegal party refused to climb down from the roof of a tram stop and groups started rioting.
It is not only at illegal raves that the Zurich police had to confront rioters over the weekend. On Saturday afternoon they skirmished with between 100 and 200 protestors who wanted to interrupt an authorised anti-abortion rally.