Many questions remain unanswered a week after the perpetrators of mass sexual assaults and thefts targeted hundreds of women at Cologne Central Station on New Year's Eve.

What we know

The assailants attacked their victims after emerging from a group of around 1,000 men, according to police information.

Police officers took the details of more than 70 people at the station during the night, according to the German police union. The union chairman in the state of North Rhine Westphalia, Arnold Plickert, said that 11 people had been detained temporarily under police powers to safeguard public order. There had also been four arrests, and 34 charges had been laid, he said.

By Friday, some 170 charges had been laid with Cologne police, with around three quarters having a sexual aspect. In many cases the female victims were robbed as well. Two cases of alleged rape are being investigated. Cologne police say they have identified more than 20 suspects that they are investigating.

The German Federal Police, who are responsible for policing the station itself, have to date recorded 32 crimes, among them assault, theft and sex crimes. The names of 31 suspects are known. According to the Federal Interior Ministry, nine of the suspects are Algerian, eight Moroccan, five Iranian, four Syrian, one Iraqi, one Serbian, one US and two are German.

Eighteen of them are asylum seekers. None of the migrants has yet been linked to a sex crime.

Arrests: Two of those held by the Cologne Police, males aged 16 and 23, were released on Friday. North Rhine Westphalia State Prosecutor Benedikt Kortz said there was a lack of evidence against them.

According to a police spokesperson, mobile phones had been confiscated. According to Kortz, three men, arrested for theft early on New Year's Day, remained in police detention on Friday.

What we do not know

It remains unclear whether crimes were in fact committed by refugees - a main sticking point in the tense debate that these crimes have triggered. Eyewitnesses, victims and police have reported the assailants were men of North African or Arab appearance.

Refugees were among those that police took the details of during the night in question, but it is not yet clear whether they are linked to any crime.

There is also as yet no clear evidence on whether or how the assailants might have organised to gather beforehand. Kortz said that this possibility was currently under investigation. A police spokesman expressed the view that it seemed "strange that it all happened by coincidence."

It is also not clear whether there is a link between events in Cologne and similar attacks in other German cities. There are mounting allegations in Hamburg - where over 100 complaints have been logged - and Dusseldorf from women laying changes of having been sexually harassed and robbed on New Year's Eve.

- dpa

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