Police opened fire on protesters and seven people were injured in rioting that erupted in downtown Rotterdam around a demonstration against COVID-19 restrictions. The Dutch city’s mayor called it “an orgy of violence.”

Mayor Ahmed Aboutaleb told reporters in the early hours of Saturday morning that “on a number of occasions the police felt it necessary to draw their weapons to defend themselves” as rioters ran rampage through the port city’s central shopping district, setting fires and throwing rocks and fireworks at officers.

“They shot at protesters, people were injured,” Aboutaleb said. He did not have details on the injuries. Police also fired warning shots.

A number of police officers also were injured in the violence and officers arrested dozens of people and expect to arrest more after studying video footage from security cameras, Aboutaleb said.

It was one of the worst outbreaks of violence in the Netherlands since coronavirus restrictions were first imposed last year. In January, rioters attacked police and started fires on the streets of Rotterdam after a curfew came into force.

The Dutch justice minister, Ferd Grapperhaus, condemned the events. “The riots and extreme violence against police officers, riot police and firefighters last night in Rotterdam are disgusting to see,” he said in a statement.

“Protesting is a great right in our society, but what we saw last night is simply criminal behaviour. It has nothing to do with demonstrating.”