German police are investigating whether the mass sexual assaults committed in Cologne on New Year's Eve are linked to a North African crime gang that has been known to them for more than 18 months.



Dusseldorf police confirmed that a special unit named "Casablanca" was investigating 2,000 individuals involved in a Dusseldorf-based organized crime network and that it has been working with Cologne police to determine whether it may be behind the recent assaults.



No arrests have been made for the crimes that have stunned Germany.



Police said Wednesday that it was investigating three suspects, but refused to elaborate. Five men taken into custody on Sunday were later found to have committed unrelated crimes.



Interior Minister Thomas de Maiziere has strongly criticized the police for its failure to bring the events on New Year's Eve under control.



More details about that night began to emerge Wednesday after false reports of 1,000 suspects circulated widely the day before.



While roughly 1,000 men did in fact gather in the area near the main train station just before midnight on New Year's Eve, police have confirmed that not all of them were involved in the attacks.



Three-quarters of the more than 100 crimes alleged were of a sexual nature and two women claimed to have been raped, police said. Victims told police the crimes were perpetrated by men of North African descent aged between 15 and 35.



Groups of up to 30 men encircled women, groped and otherwise sexually assaulted them and in the majority of cases stole their belongings. Police and crime experts have confirmed that this diversion tactic to commit theft has been known to them for some time.



Similar crimes were committed by men with "Mediterranean or Arab looks" in Hamburg, where 53 complaints were filed including 39 allegations of sexual assault and 14 of theft. However, police in the northern city confirmed on Wednesday that it had no indication of a link to the Cologne attacks.



Although Cologne Mayor Henriette Reker has said there is no indication the suspects are refugees, the crimes have triggered a fierce debate in Germany about the repercussions of allowing 1.1 million migrants to enter the country over the course of 2015.



Reker came under fire on Wednesday after suggesting a code of conduct for women in response to the mass assaults.



People took to social media under the hashtag #EineArmlaenge - German for "an arm's length" - to lambast Reker's suggestion that women keep a certain distance from strangers on the street and remain within groups to avoid being singled out.



Reker, who was stabbed on the campaign trail in October because of her pro-refugee stance, has been accused of victim-blaming. Her critics argue that her focus should be on ramping up security and bringing the attackers to justice.

By Friederike Heine