Marking a sharp jump from the caseload of 379 given on Saturday, police said some 516 complaints had now been lodged, including 40 percent that are related to sexual assault.
Witnesses described terrifying scenes of hundreds of women running a gauntlet of groping hands, lewd insults and robberies in the mob violence.
Even though no formal charges have been laid, Cologne police have said those suspected over the New Year's rampage near the city's railway station were mostly asylum seekers and illegal migrants from North Africa.
The scale of the Cologne assaults has shocked Germany and put a spotlight on the 1.1 million asylum seekers who arrived in the country last year.
It has also fuelled fear, with a poll published by Bild am Sonntag newspaper saying that 39 percent of those surveyed felt police did not provide sufficient protection, while 57 percent did.
And just under half (49 percent) believed the same sort of mob violence could hit their hometown, reported the newspaper which headlined its article with the question: "Is the New Year Eve scandal the result of wrong policies?"
Turning away from her mantra of "we will manage this" over the record migrant influx, Merkel has been forced to change tack.
She took a tough line on Saturday, saying she backed changes to the law to make it easier to expel asylum seekers convicted of a crime.
"If the law does not suffice, then the law must be changed," she said.
"Cologne has changed everything, people now are doubting," said Volker Bouffier, vice president of Merkel's CDU party.
- AFP