German Chancellor Angela Merkel, right, watches an exercise of a group of combat divers during her visit to Naval Base Command in Kiel, Germany.

A 26-year-old Algerian man has become the first person arrested in connection with a string of sexual assault during New Year’s celebrations in Cologne that sparked a debate about Germany’s ability to integrate migrants.

Prosecutors said that the unidentified asylum-seeker was arrested at a refugee home in the nearby town of Kerpen over the weekend. He is accused of groping a woman and robbing her cellphone, prosecutor’s office spokesman Ulrich Bremer told The Associated Press.

Two other Algerian asylum-seekers, aged 22 and 24, were also arrested in Kerpen and the western city of Aachen, respectively, over the weekend, both for robbery, Bremer said. The number of people accused of committing crimes in Cologne at New Year’s now stands at 21, of whom eight are in detention, he said.

Almost three weeks after the incident, 838 people have filed criminal complaints, including 497 women alleging sexual assault. Some of the victims have jointly filed a single complaint, so that the number of alleged crimes stands at 766, of which 381 are sexual offenses, including three rapes.

The scale and nature of the crimes in Cologne, coupled with police descriptions of the perpetrators as being part of a large crowd of drunken men of “Arab or North African” origin, has fanned the debate about Germany’s approach to migration. Almost 1.1 million asylum-seekers arrived in the country last year, many of them from countries where women face greater discrimination than in Germany.

Meanwhile, a group of conservative lawmakers urged Angela Merkel to reverse her open-door refugee policy as a poll showed a slide in support for her bloc on Tuesday, raising the stakes for a German chancellor exposed by deep rifts in her right-left coalition.

With three closely watched regional elections looming in March, Merkel is facing the toughest spell of her 10-year chancellorship over her handling of the refugee crisis.

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