Right wing political parties have rounded on Angela Merkel after 1,000 men of 'Arab and North African origin' were said to have carried out a wave of sexual assaults at Cologne train station.

German police are hunting for the men, who are accused of rape and numerous sexual assaults at the main station, next to the city's famous cathedral on New Year's Eve.

About 90 women have reported being raped, robbed, threatened or sexually molested at the New Year's celebrations by young, mostly drunk, men, police said today.

Scroll down for video

Fireworks are thrown into the crowd outside Cologne's main station, prompting members of the public to flee

Another firework is let off as a group of men watch on laughing in a video posted online to YouTube

Witnesses and women who reported being attacked described the men as looking as if they were from 'the Arab or North African region', police chief Wolfgang Albers said.

The incident has stirred strong emotions in Germany and has fuelled calls by right-wing groups to halt the admission of immigrants.

Germany took in just over a million last year, far more than any other European country.

The right-wing Alternative for Germany (AfD), which has gained in polls in part at Merkel's expense thanks to a campaign against refugees, said she should close the border.

'Mrs Merkel, is Germany "colourful and cosmopolitan" enough for you after the wave of crimes and sexual attacks?' tweeted AfD chief Frauke Petry.

Mrs Merkel responded on Tuesday, urging people to respect strangers.

'We... respect everyone, even if we don't know them. That is the case not only for Germans, but for everyone.'

However, Cologne mayor Henriette Reker said there was no reason to believe that people involved in the attacks were refugees.

After a crisis meeting, Cologne mayor Reker said the perpetrators had acted 'absolutely unacceptably' and women must continue to join celebrations but with more protection.

Reker was stabbed in the neck and seriously hurt in October, just a day before she was elected mayor. Police said that attack appeared to be motivated by her support for refugees.

'We don't currently have any suspects, so we don't know who the perpetrators were,' Cologne's police chief Wolfgang Albers told reporters. 'All we know is that the police at the scene perceived that it was mostly young men aged 18 to 35 from the Arab or North African region.'

Heiko Maas, the justice minister, said: 'We will not accept the disgusting attacks on women. All perpetrators must be held to account.'

Some politicians have suggested installing more security cameras and increasing police numbers at traditional carnival celebrations next month when the city closes down for five days of drunken street parades and parties.

Mayor Henriette Reker and President of Cologne Police Wolfgang Albers (right) hold a news conferenece after about 90 women reported being robbed, threatened or sexually molested during New Year's Eve celebrations

German police are hunting for a group of up to a 1,000 men 'of Arab and North African origin' who are said to have sexually assaulted numerous women and caused trouble at Cologne's main station

One of the victims, named only as 'Katja L', gave a harrowing testimony of her ordeal.

'When we came out of the station, we were very surprised by the group that met us there'. She said the group was 'exclusively young foreign men,' she told Der Express.

'We then walked through this group of men. There was an alley through [the men] which we walked through.'

She described the moment she 'felt a hand on my buttocks, then on my breasts, in the end'.

'I was groped everywhere. It was a nightmare. Although we shouted and beat them, the guys did not stop. I was desperate and think I was touched around 100 times in the 200 meters,' she said.

'Fortunately I wore a jacket and trousers. A skirt would probably have been torn away from me'.