Hundreds of people gathered in Cologne Tuesdaynight to protest against the attacks.
"The perpetrators must be caught and brought tojustice."
Police say more than a thousand men–many of themreportedly of northern African and Middle Easterndescent-had gathered in front of the cathedral onNew Year's Eve.
They threw firecrackers into the crowds-before splitting into groups and surrounding lonewomen, sexually assaulting and robbing them.
Around 90 women have complained to police.
The attacks have poured fuel on the already-heated debate over immigration.
Alexander Marguier-deputy editor of the political magazine Cicero-said via Skype from Berlinthat many Germans are blaming the government's immigration policy.
“You have to see the fact also that this has not happened before.
You know, such a big crowd in the main station of Cologne and also in other German cities, wehaven't seen this before.
So there might be a link to this migration policy."
More than a million migrants arrived in Germany in 2015.
The government says it's crucial to identify the attackers.
"General suspicions against refugees that are based on leads saying the perpetrators looked likepeople from North Africa are just out of place, but, we should not skip the debate aboutwhether they are refugees or not."