ZURICH - What began as an illegal open-air party near Hardplatz ended in some of the worst violence the Zurich city police have faced this year. More than 100 people, several of them masked, turned on the officers sent to clear the gathering in the night from Saturday to Sunday, attacking them with paving stones, bottles and mortar fireworks.

Neighbours had reported the party shortly after 23:00, and the city police at first tolerated the crowd of around one hundred. That changed when firecrackers went off, building facades and parked vehicles were damaged and noise complaints multiplied. Officers ordered the gathering to disperse within ten minutes.

Retreat under a hail of stones

Instead of leaving, part of the crowd barricaded itself in the Hardplatz underpass and charged the police line. Hit by bottles and paving stones, the officers first had to pull back, before coming under mortar fire in which some projectiles exploded at head height. The attackers set fire to around 20 waste containers, blocking the underpass and entire streets.

To retake the area, the police deployed a water cannon, rubber projectiles and tear gas. Calm returned only around 3:00 in the morning. The balance sheet is heavy: one injured police officer, several badly damaged emergency vehicles and property damage that the city is still counting.

Prepared for a fight

The city police suspect the confrontation was no accident. The stock of stones and fireworks gathered behind the barricades points to preparation, a spokesperson said, and investigators are now reviewing footage from the underpass and nearby streets. Many questions remain open, including who called for the party and how the crowd organised itself so quickly.

The night stands in sharp contrast to the weekend's other gatherings. In Bern, an unauthorised anti-capitalism rally of about 1,000 people ended without major incidents on Sunday, and a week earlier around 1,000 marchers crossed Zurich in a peaceful Gaza demonstration. The difference at Hardplatz, police say, was a crowd that came ready to fight.