As outrage grew in Germany over the assaults, which included two alleged rapes and several accounts of groping during New Year's Eve festivities in Cologne, Merkel said citizens were right to raise serious questions.
She pledged strong action and stressed that "we must also speak again about the cultural fundamentals of our co-existence".
Some 121 complaints have been filed so far, with police saying they are investigating "16 young men... Mostly of North African origin" although no one has yet been charged.
About three-quarters of the cases involved sexual offences, while others related to theft or bodily harm.
Welcoming the fact that large numbers of alleged victims have come forward, Merkel said there were "very serious questions that go beyond Cologne" for Germany.
The attacks have shown that there is in "some quarters, contempt for women," she said.
"We need to confront that with utmost determination," Merkel said, adding that she did not believe that the cases were isolated.
Although authorities have said there are no indications that the perpetrators of the assaults were asylum seekers, critics of Merkel's open-door approach to those fleeing war have seized on the opportunity to draw a link.
"We need to re-examine if everything necessary has been done with regards to expulsions to send a clear signal to those who do not respect our law."
The assaults plaguing the Rhineland city during New Year's festivities were not isolated, with the northern port city of Hamburg also hit.
Some 70 complaints of sexual assaults have been filed, Hamburg police said, with 23 of those victims also reporting that they'd been robbed.