A German court on Friday tried the first sexual assault case from chaotic New Year's celebrations in the western city of Cologne that heightened public fears about the country's record migrant influx.

The 26-year-old Algerian man in the dock was accused of forming part of a threatening mob of about 10 men who encircled, harassed and groped a woman, and of stealing her cellphone.

Prosecutors charge that several perpetrators over two to three minutes grabbed their 26-year-old victim's buttocks and other body parts "with sexual motivation" in the city's central railway station while the accused snatched the phone from her purse.

Also on trial in Cologne was the man's 23-year-old brother, accused of stealing a cellphone from another woman under similar circumstances. The brothers are also accused of trying to break into a car last December.

The Cologne attacks -- committed in a dense crowd of mostly Arabic and North African men -- appalled Germany and sharpened public concern about the arrival of over one million mostly Middle Eastern asylum seekers, with far-right groups railing against "sex jihadists" and "rapefugees".

The ugly scenes also cast a harsh spotlight on the city's police who initially failed to prevent the violence then tried to play down the extent of the chaos for several days.

As the attacks gained wider media coverage, more women came forward. Prosecutors have now received some 1,170 criminal complaints, including 492 accusations of sexual assault.

Nine men have so far been sentenced in Cologne, all for property crimes.

A key suspect in the Cologne sexual violence, a 19-year-old Moroccan man, is set to face trial after he was spotted shoplifting in southern Germany and arrested across the border in Switzerland last week.

Another Moroccan man is on trial in the western city of Duesseldorf over a New Year's attack there in which he allegedly groped an 18-year-old woman encircled by some 15 to 20 men.

Source :AFP