A drug check in Stuttgart, Germany, turned violent as hundreds of people started vandalizing shops and attacking police officers.

Twenty people were arrested and four officers injured in the attacks, police said.  Authorities started the drug search as groups of people partied in a park late Saturday.

Goods lie on the floor after people broke into a shop on Marienstrasse in Stuttgart, Germany, Sunday, June 21, 2020. Dozens of violent small groups devastated downtown Stuttgart on Sunday night and injured several police officers, German news agency DPA reported. (Julian Rettig/dpa via AP)

Some people in the crowd became enraged, fighting police and damaging nearby shops. Photos and video circulated on social media, showing both the actions of rioters as well as the police response.

Goods lie on the floor after people broke into a shop on Marienstrasse in Stuttgart, Germany, Sunday, June 21, 2020. Dozens of violent small groups devastated downtown Stuttgart on Sunday night and injured several police officers, German news agency DPA reported. (Simon Adomat/dpa via AP)

Baden-Württemberg’s Interior Minister Thomas Strobl told WELT, a German news channel, that the level of violence was “never seen before” in the city. He promised to prosecute rioters to the fullest extent of the law.

“We will not tolerate such events in Baden-Württemberg,” he said. He also thanked police for their efforts during a “difficult and dangerous operation.”

Stuttgart police said 200 officers responded to the incident.

The footage shows people attacking police and hurling objects, including  bottles and cobblestones, at police vehicles. A number of storefronts were smashed and there were reports of looting.

Police said it is not clear who was responsible for the riot.

Mayor Fritz Kuhn tweeted about the “sad Sunday for Stuttgart,” as the unrest continued into the early morning hours.  He condemned the riot, saying he was “shocked” by the violence.

“One thing must be clear: There must be no lawless rooms in Stuttgart.”

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Police have encouraged witnesses to upload any videos that might aid in the investigation.

The Associated Press contributed to this report.