German police have identified three suspects in connection with attacks on women at New Year celebrations in the city of Cologne but have not yet made any arrests, the interior minister of the state of North Rhine-Westphalia (NRW) said on Wednesday.

About 90 women reported being robbed, threatened or sexually molested at New Year celebrations outside the city's cathedral by young, mostly drunk, men, police said on Tuesday, in events they described as "a new dimension in crime". The police chief in Cologne has said the perpetrators appeared to be of "Arab or North African" origin, prompting right-wing groups to condemn the government for its welcoming stance towards refugees fleeing war in Syria and elsewhere.

NRW Interior Minister Ralf Jaeger said he expected a "very detailed report" from the police this week but declined to give further details about the investigation. Police said the attacks occurred when about 1,000 men split into gangs as officers cleared a square to stop fireworks being thrown from the top of steps into the crowd below.

Government officials have cautioned against putting foreigners and refugees under "blanket suspicion" while Cologne mayor Henriette Reker has said there is no reason to believe those involved in the attacks were asylum seekers.

Germany took in about a million asylum seekers over the past year and many more are expected to arrive during 2016. German officials are at odds over how to respond to the assaults in Cologne.

Federal Interior Minister Thomas De Maiziere has criticised local police for not having intervened during the New Year celebrations to prevent further assaults on women. On Wednesday De Maiziere said the government should discuss whether to make it easier for the authorities to deport asylum seekers who break the law.

Jaeger said it was a "matter of form" to wait for the results of the police investigation before passing judgement. Jaeger also distanced himself from Reker, who sparked an outcry by suggesting on Tuesday that women should keep unknown men "at arm's length" to avoid being assaulted. "This twists the role of victim and offender a bit," Jaeger said, adding it was not up to women to avoid being assaulted.

Around 150 people gathered in front of Cologne's cathedral on Tuesday evening to protest against violence against women. One of them held a sign saying: "Ms Merkel where are you? What do you say? This scares us!" Chancellor Angela Merkel has expressed shock at the attacks.