Women have made at least 90 criminal complaints to police about the harassment by gangs at Cologne's main railway station on Thursday night.
Germans have been shocked by the scale of the attacks, involving many groups of drunk and aggressive young men.
Witnesses and police said the men were of Arab or North African appearance.
Cologne sex attacks: Merkel disgust at New Year gang assaults - BBC News
Cover-up claim over NYE mass sexual assaults - The Local