COLOGNE, Germany - An internal report by German police describes how women in the western city of Cologne had to run through mobs of drunken men who attacked them during New Year's celebrations, an experience likened to "running the gauntlet".

A crowd of about 1,000 men - described by the city's police chief as being "largely from the North African or Arab world" - had reportedly gathered outside the main train station that night.

The perpetrators are said to be of "north African" appearance although Cologne police have denied asylum seekers are involved.

Mayor Henriette Reker said she expected police to analyze what went wrong and "draw consequences from that".

Chancellor Angela Merkel expressed outrage over the "disgusting attacks" and the interior minister was asked about the police response on national TV.

On Thursday, Bild newspaper and Spiegel Online quoted an internal police report detailing how officers were powerless to hinder the terrifying rampage on New Year's Eve.

The mayor of a German city where scores of women were allegedly threatened or assaulted on New Year's Eve is facing criticism for comments she made about the attacks.

But police union chief Rainer Wendt said a lack of resources had meant that the Cologne force had been unable to clear the square properly.

Police have received more than 100 complaints - three-quarters of them of a sexual nature - including two allegations of rape.

As the women fled, the men pressed themselves against them, stealing mobile phones, wallets and other personal possessions from their pockets as they passed.

Gangs of young, mostly drunk, men are being hunted on suspicion of the assaults.

People sentenced to one year or more in prison can be deported under existing laws "irrespective of their origin", Heiko Maas told Funke Media Group.

Some of these groups, police said, then targeted women, harassing them, mugging them, and brutally groping them. And reports indicate that at least eight of the suspects who have been identified were in the country as asylum seekers.

WOMAN (TRANSLATED): All of a sudden these men around us began groping us, they touched our behinds and walked in step with us.

The incidents have fuelled calls from right-wing groups to shut down migration to Germany, which has taken in more than a million people in the previous year, mostly from Middle Eastern war zones. She offered suggestions on how women should behave to avoid similar attacks, including remaining "within your own group, and asking bystanders to intervene or to help as a witness". But authorities say there is no evidence that refugees who arrived in Germany past year were involved in the assaults, AFP reported.

But she disagreed with those who blamed the latest wave of refugees for the assaults.

Reker later said that people from "other cultures" should also be educated on acceptable conduct in public, but emphasized that the incident shouldn't automatically be linked to recent immigrants.