Several Pakistanis and Syrians have been injured in attacks by gangs of people in Cologne, the German city where hundreds of assaults on women during New Year's celebrations have been reported, according to police.

Local newspaper Express reported that the attackers were members of hooligan gangs who, via Facebook, arranged to meet in Cologne's business district to start a "manhunt" for foreigners.

Police say that they are still investigating whether the attacks were racially motivated and whether there was any link to the New Year assaults.

READ MORE: German MPs to discuss New Year's Eve sexual assaults

Cologne police said at least 11 foreigners, including Pakistanis, Guineans and Syrians, had been injured on Sunday evening in attacks.

The assaults on women in Cologne and other German cities have prompted more than 600 criminal complaints, with the police investigation focusing on asylum seekers.

The incidents, ranging from theft to sexual molestation, have kicked off a highly charged debate in Germany about Chancellor Angela Merkel's open-door policy on refugees and migrants, more than one million of whom entered the country last year.

Merkel said on Monday that Europe was "vulnerable" in the refugee crisis because it was not yet in control of the situation to the extent that it would like to be.

"Now all of a sudden we are facing the challenge that refugees are coming to Europe and we are vulnerable, as we see, because we do not yet have the order, the control, that we would like to have," Merkel said at a business event in Mainz, near Frankfurt.

The attacks on women in Cologne have prompted a debate about tougher rules for migrants and refugees who break the law, faster deportation procedures and increased security measures such as more video surveillance in public areas and more police.

A regional parliamentary commission in the state of North-Rhine Westphalia, whose largest city is Cologne, was to question police and others on Monday about the events on New Year's Eve.

Also on Monday, the anti-Islam political movement Pegida's supporters threw bottles and firecrackers at a march in Cologne on Saturday before being dispersed by riot police.