Chanting "Merkel out" and waving placards with slogans like "Rapefugees not welcome", xenophobic German PEGIDA protesters vented their fury Saturday against migrants after mass sexual assaults on New Year's Eve.

Amid clashes with police, the far-right protesters took aim at Chancellor Angela Merkel, accusing her of allowing migrants to run amok through her liberal stance towards those fleeing war

Tensions escalated when followers of the movement -- about half of them violence-prone hooligans, according to police -- marched and hurled beer bottles and fire crackers at police, screaming "where were you on New Year's Eve?"

Riot police beat back the agitated protesters with batons, teargas and water cannon in clashes that left three police and one journalist injured and in which police detained multiple demonstrators.

"Merkel has become a danger to our country. Merkel must go," one speaker earlier told the 1,700-strong crowd, which loudly echoed the call, expressing their anger at Germany's 1.1-million-strong migrant influx last year.

"Tolerance is the final virtue of a dying society," read another banner in the protest, organised by the local chapter of PEGIDA, the self-styled "Patriotic Europeans Against the Islamisation of the Occident".

The heated protest was held in the Cologne railway station area that was the scene of the New Year's Eve assaults, at which witnesses described the perpetrators as people of "North African or Arab" appearance.

Cologne police have come in for broad criticism for failing to stop the violence and being slow to report on it afterwards, a scandal that Friday claimed the scalp of city police chief Wolfgang Albers.

By Saturday police had received 379 criminal complaints of groping, assaults, thefts and two rapes. Federal police have said that a majority of suspects identified so far were of foreign origin, inflaming a debate over Germany's ability to integrate the influx of refugees.

One PEGIDA speaker, a mother of four introduced only as Christiane, told the rally: "These women who fell victim will have to live with it for a long time. I feel like my freedom has been robbed."

PEGIDA started life over a year ago as a xenophobic Facebook group, initially drawing just a few hundred protesters in the eastern city of Dresden before gaining strength, peaking with rallies of 25,000 people.

Interest subsequently began to wane following overtly racist comments by founder Lutz Bachmann, and the surfacing of "selfies" in which he sported a Hitler moustache and hairstyle, but PEGIDA has seen a revival with the record influx of migrants.

The PEGIDA protesters Saturday were greeted by 1,300 leftist demonstrators who staged a counter-protest, chanting "Nazis raus!" (Nazis out!), as hundreds of the 2,000 deployed police separated the crowds.

"There is nothing right about Nazi propaganda," read one sign, while another said "Fascism is not an opinion, it is a crime".

"We are there to tell them to shut up. It is unacceptable for PEGIDA to exploit this horrible sexual violence perpetrated here on New Year's day and to spread their racist nonsense," said Emily Michels, 28.

Half a dozen Iraqi and Syrian refugees were among the counter-demonstration, together with a Jordan-born woman running their local shelter, Dana Khamis.

"I told them the demonstration is about women's rights and against sexism and against facism, and they said they wanted absolutely to be part of it," said Khamis, 27.

Earlier, up to 1,000 women staged a noisy protest carrying signs demanding "No violence against women" and "No means no! It's the law! Stay off of us!", banging pots and blowing whistles outside Cologne's famed Gothic cathedral.

"We want our safety back. We are against all violence against women," said protest organiser Martina Schumeckers, 57, a musician.

"I am standing here for all mothers, daughters, granddaughters, grandmothers, for them all to be able to move around safely, especially in our Cologne."