Authorities in Cologne announced on Monday that they arrested a man for allegedly committing a sexual assault during New Year's celebrations in Cologne.

A 26-year-old Algerian man stands accused of groping a woman and stealing her mobile phone, said Cologne's chief prosecutor, Ulrich Bremer. He is the first to be arrested for sexual assault charges.

The unidentified asylum-seeker was arrested along with a 22-year old Algerian over the weekend at a refugee home in Kerpen, 30 kilometers outside of Cologne, Bremer said. The other suspect was in possession of a cell phone which was stolen during the attacks at Cologne's central train station.

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Speaking with the Associated Press news agency, Bremer said that nearly 500 women have come forward with allegations of sexual assault, including three cases of rape.

So far, 21 people have been charged with non-sexual offences, and eight of the suspects are also awaiting trial. Most of them have been accused of theft.

On New Year's Eve, witnesses at the city's main train station and cathedral described women being groped, as well as subjected to lewd insults and robbery. Most of the culprits were said to have been of a North African or Middle Eastern appearance.

The reports have fueled protests across Germany and harsh criticism of Chancellor Angela Merkel's open door policy for refugees and migrants.

rs/kms (AP, AFP, dpa)