Between 500 and 1,000 men robbed and sexually assaulted women in Cologne, Germany on New Year’s Eve in a coordinated attack, according to the city’s police. Police chief Wolfgang Albers described ”a completely new dimension of crime” carried out by perpetrators of apparent Arab or North African descent. The assaults are being cited by German anti-immigration activists as proof that the country’s intake of 1 million refugees is leading to anarchy.

The assaults took place at the city’s iconic train station and outside the adjacent Cologne Cathedral; both are typically crowded tourist destinations where pickpocketing is a known risk. At the train station, the assailants reportedly threw firecrackers into the crowd (German) to create chaos before rushing at their victims to violently grope and rob them (German). A volunteer policewoman was among those sexually molested, and at least one rape reportedly occurred.

At least 60 women filed official police claims in the aftermath, according to Germany’s edition of The Local. Some members of the public are outraged over a perceived cover-up of the attacks, and saying it took too long for national news outlets to report what happened in full detail, including the ethnicity of the alleged assailants. Anabel Schunke, a writer for the Huffington Post in Germany, suggested (German) that racial details were left out so that public sentiment would not turn against refugees.

German justice minister Heiko Maas said the ethnicity of the attackers was irrelevant. “The rule of the law does not look at where someone comes from but what they did,” he said at a press conference, as reported by the New York Times. “We will investigate what circles the perpetrators may have come from.”

The BBC reports that local politicians are now concerned that a similar or worse attack might take place in February during Cologne’s Carnival festivities days, which brings rowdy crowds to the city’s center.