German politicians waged a heated debate yesterday over whether to make it easier to expel convicted asylum seekers, after a series of sexual assaults on New Year's Eve blamed on men of foreign origin.

Authorities have said there is no concrete proof that the perpetrators of the attacks in Cologne were asylum seekers, but critics of Chancellor Angela Merkel's open-door approach to those fleeing war have seized on the opportunity to draw a link.

Victims described their attackers as being "Arab or North African" in appearance, and 16 suspects are being investigated, but no one has yet been charged.