German police say the number of criminal complaints filed after the events on New Year's Eve in Cologne has risen to 516 - 40% of which relate to allegations of sexual assault.
Police in Cologne investigating the crimes are focussing on people of North African origin, they say.
On Sunday evening six Pakistanis and a Syrian man came under attack in the centre of the western German city.
Angela Merkel's immigration policy has come under criticism since the attacks.
Around 1.1 million asylum seekers arrived in Germany in 2015.
The scale of the assaults on women in Cologne and other German cities on 31 December has shocked the country, and police handling of the events has been sharply criticised.
Riot police used water cannon to disperse anti-migrant protesters in Cologne on Saturday.
The attacks on Sunday took place in the early evening. In the first, a group of around 20 people attacked six Pakistanis, two of whom had to be treated in hospital.
Separately, five people injured a Syrian man who did not need hospital treatment.