“Where were you on New Year’s Eve?” one protester yelled at police “Why didn’t you protect those women?”

Thirty-one people, most of them North African or Middle Eastern countries, have been charged in the attacks. Of those, 18 have been identified as asylum-seekers.

Cologne police said they received a total of 379 complaints about New Year’s Eve in Cologne, with about 40% being investigated as sex crimes. Other European cities reported similar rashes of sex crime reports.

German Chancellor Angela Merkel has condemned the attacks in Germany as “disgusting, criminal acts” deserving of a decisive response. But she did not back down on her commitment to welcome refugees who obey German laws and pledge to integrate into German society.

In Cologne, where many of the attacks took place, a police spokesman confirmed that Chief Wolfgang Albers was fired Friday. Albers’ dismissal came amid criticism of his department’s handling of the violence.

One victim of the Cologne violence told CNN there were too few police on the streets to prevent attacks.

“We ran to the police. But we saw the police were so understaffed,” the victim said. “They couldn’t take care of us and we as women suffered the price.”

Spiegel Online reported that groups of men prevented officers from reaching those crying out for help.

“The events of New Year’s Eve like a spotlight once more highlighted the challenge we face in a new aspect that we had not really looked at before,” Merkel said Saturday in Mainz, at a meeting of her conservative CDU Party.

Merkel garnered international acclaim for her decision to welcome many of the hundreds of thousands of Middle Easterners who have made the journey to Europe this year in search of safety, food, work and a better life.

But Merkel stressed Saturday that Germany’s welcome was not unconditional.

“We, of course, expect from the refugees who come to us, those seeking protection, that they have the will to integrate, that they strive for integration,” she said.

Her response showed a determination to avoid repeating what are broadly viewed within Germany as the mistakes officials made with regard to Turkish “guest workers” after World War II. Because it was assumed that arrangement was temporary, virtually no attempt was made to learn (or teach) the language, customs and mores of the new home country.

The mistakes of that era echo through Germany to this day. Generations later, some families of Turkish origin living in Germany do not speak German, and forests of satellite dishes are all aligned to receive Turkish TV broadcasts. Many young third- or fourth-generation Turks lack a sense of belonging, a sense of being German, even though their grandparents were born in the country.

Cologne mayor criticized for advice to avoid men

And Merkel continued to say the newcomers were welcome.

Tough prosecution of wrongdoing, she said, “is in the interest of citizens of Germany, but it is just as much in the interest of the large majority of refugees who are here with us and, therefore, it is absolutely right.”

Those who break German laws may forfeit their right to residency and to asylum, she said.

Germany is going through experiencing recriminations over who should have prevented the attacks and whether someone was asleep at the wheel.

Interior Minister Thomas de Maiziere has criticized the response of Cologne police, and German Justice Minister Heiko Maas was among many who expressed disapproval of Cologne Mayor Henriette Reker for advising women to keep “more than an arm’s length” away from unknown men.

Reker later said the comments had been taken out of context.

Cologne police spokeswoman Christoph Gilles told reporters Friday that 170 criminal complaints had been filed related to the apparently coordinated attacks, “at least 120 of which have a sexual angle.”

An 80-person investigative team is looking at 250 videos with about 350 hours of footage, Gilles said.

The 31 suspects charged include nine Algerian nationals, eight people from Morocco, five from Iran and four from Syria, German interior ministry spokesman Tobias Plate said. Two are German citizens, while one each comes from Iraq, Serbia and the United States.

Other German cities experienced similar attacks the same night, including the northern city of Hamburg, where more than 50 incidents were reported.