German state interior minister Ralf Jaeger has said migrants were almost exclusively responsible for the attacks on women in Cologne on New Year's Eve.
More than 100 women reported being threatened, robbed or molested during the city's celebrations.
The minister's comments come amid reports a group of Pakistanis and a Syrian were violently attacked by about 20 unknown assailants on Sunday in the city.
Police have used a water cannon to disperse protesters in the German city of Cologne.
Supporters of anti-immigration right-wing movement Pegida have been taking part in a demonstration following mass assaults on women on New Year's Eve.
Around 1,700 police officers have been deployed during the protest, and there were reports of scuffles between authorities and those taking part.
The German Chancellor wants increased powers to block foreigners from being granted asylum if they have any sort of criminal record.
Around 400 people gathered in Cologne to demonstrate against violence against women following a wave of assaults on New Year's Eve.
Authorities in Cologne are holding crisis talks on Tuesday after a string of sexual assaults by large gangs of men.