German authorities have expressed shock over a rampage of an “unprecedented scale” in the centre of Stuttgart, where hundreds of partygoers ran riot overnight and into Sunday, breaking shop windows, plundering and attacking police. Two dozen people, half of them German nationals, were provisionally arrested and police reported 19 officers hurt. “They were unbelievable scenes that have left me speechless. In my 46 years of police service, I have never experienced this,” said the Stuttgart police chief, Franz Lutz. Tensions built up shortly after midnight when officers carried out checks on a 17-year-old German man suspected of using drugs, said Stuttgart’s deputy police chief, Thomas Berger. Crowds who were milling around at the city’s biggest square, the Schlossplatz, immediately rallied around the young man and began throwing stones and bottles at police. The groups, mostly men, also used sticks or poles to break the windows of police vehicles parked in the area. “I sharply condemn this brutal outbreak of violence, these acts against people and things are criminal action that must be forcefully prosecuted and condemned,” said Winfried Kretschmann, Baden-Württemberg’s state premier, in a statement. At the height of the clashes, some 400 to 500 people joined in the battle against police officers and rescue workers. As officers pushed back against the crowd, they broke up into small groups, carrying on their rampage around the city centre, breaking shop windows and looting stores along nearby Königstraße, a major shopping street. One jewellery shop was emptied and a mobile phone shop ransacked, according to regional broadcaster SWR. Nine shops were looted in all, and 14 others were damaged. After smaller-scale clashes broke out in the city centre last week between police and groups of young people, officers bulked up their deployment with an extra 100-strong team. But the scale of the violence overwhelmed the officers, forcing them to call in reinforcements from other parts of the state. It took them four and a half hours to quell the violence, which the Social Democrat regional MP, Sascha Binder, described as “civil war-like scenes”. Police have ruled out any political motives for the rampage, describing the perpetrators as people from the “party scene or events scene”. An unusually large number of people were in the city centre to enjoy the summer evening because discos and clubs were still shut because of the coronavirus pandemic, Stuttgart’s mayor, Fritz Kuhn, said. Some of the rioters were under the influence of alcohol and others may have been driven by “the addiction of putting a little film on social media”, he said. Asked about the nationalities of the 12 non-Germans who were detailed, Berger said they came from a range of countries, from Croatia and Portugal to Afghanistan and Somalia. The interior minister for the region, Thomas Strobl, said the disturbances were of “an unprecedented nature” and vowed to “use all available means available under the rule of law to go after the rioters”.