Cologne prosecutors today said the unidentified asylum-seeker was arrested at a refugee home in the nearby town of Kerpen over the weekend.
The man is the first person to be held on sexual offence related charges, after a string of assaults in Cologne that sparked a debate about integration in Germany.
Prosecutor's office spokesman Ulrich Bremer told The Associated Press that 497 women have come forward alleging sexual assault, including three rapes, during New Year's. The suspect in custody is accused of groping a woman and robbing her cellphone.