Germany is at a near boiling point after horrific mass attacks on women in one of its oldest major cities

The controversy over what German Chancellor Angela Merkel has called the most complex challenge of her 10 years in office has reached a near boiling point after mass New Year's Eve attacks on women in the city of Cologne.

A police report (in German) on the attacks released Monday detailed rampant sexual assault and other attacks that it attributed to gangs of mostly migrant men, many of whom reportedly came from Africa and the Middle East.

The attacks have further inflamed the contentious debate in Germany over Merkel's "open-door" policy toward refugees fleeing violence in the Middle East. And they have started reverberating across the Atlantic Ocean.

The number of criminal complaints stemming from the New Year's Eve mayhem in Cologne and smaller attacks in other German cities is greater than 600. About 40% of those complaints relate to allegations of sexual crimes, the BBC reported.

More than 1,000 people - mostly men - gathered in the Cologne's central train station on New Year's Eve before breaking up into smaller groups that molested and robbed women, according to the report from the interior ministry of Germany's North Rhine-Westphalia.

The criminal complaints range from theft to sexual molestation and rape, as a team of more than 100 law-enforcement officers continues to investigate. The focus, however, has mainly been on asylum seekers and migrants from North Africa, according to the interior ministry's report.

More than 30 suspects have been linked to the attacks so far, with at least 22 being asylum seekers, according to USA Today. The suspects are mostly from Algeria and Morocco. In total, the police traced the suspects' citizenship to eight countries, including Iran, Syria, and the US. At least nine of the suspects arrived in Germany since September.

The government report into the Cologne attacks, released Monday, said Germany had not previously been exposed to such a massive combination of sexual violence and robbery.

The report said carrying out "taharrush gamea," which is Arabic for group sexual harassment in crowds, was believed to be the motive for the attack. The report compared it to similar incidents that occurred in Cairo's Tahrir Square during the Arab Spring and Egyptian revolution. A joint federal and state group has been set up to study and combat taharrush gamea.

There have since been protests against Merkel's open-door policies, which have allowed more than 1 million migrants and refugees to enter the country since last year.

US Republican presidential front-runner Donald Trump weighed in on the crisis Monday during a campaign event in New Hampshire, saying Merkel, with her refugee policy, had gone "off the reservation."

"The rapes. The riots. What's happening is unbelievable. It's unbelievable. Unthinkable," Trump said.

"They have a problem," he added. "She went off the reservation. I don't know what happened to her."

Retaliatory violence against foreigners has also stemmed from the attacks. Gangs of people in Cologne attacked six Pakistani men and one Syrian man in Cologne near the site of the original attacks Sunday, German police officials said. A local newspaper reported those attackers arranged to meet in downtown Cologne on Facebook to start a "manhunt" of foreigners, according to Reuters.

Pope Francis commented on the attacks and subsequent backlash, saying Europe's "humanistic spirit" was at risk of being undermined, the BBC reported. He said Europe must create a balance between protecting its citizens and helping those in need, acknowledging that he thought the "immense influx" of migrants was leading to problems.

Some have blamed a slow police response for why the assailants in Cologne were able to attack so many people. North Rhine-Westphalia's interior minister, Ralf Jaeger, has accused the police of making "serious mistakes."

Jaeger pushed Cologne's police chief, Wolfgang Albers, into early retirement because of those mistakes.

"After the intoxication with drugs and alcohol came violence," Jaeger said, per the BBC. "It culminated in the acting out of fantasies of sexual omnipotence. That must be severely punished."

The attacks in Cologne were most likely premeditated, Germany's justice minister, Heiko Maas, said.

"My suspicion is that this specific date was picked, and a certain number of people expected," he said.

But Maas said the Cologne attacks did not mean migrants and refugees couldn't be integrated into German society. He said any rhetoric to the contrary was "complete nonsense" from the far right.

The far-right, anti-Islam political movement Pegida, which stands for Patriotic Europeans Against the Islamization of the West, has been at the forefront of the protests in the aftermath of the Cologne attacks. On Saturday, riot police - in much larger numbers than were present during the Cologne attacks - used water cannons to flush out Pegida protesters in Cologne.

Pegida protesters were met with left-wing counterprotests, with both sides throwing objects like bottles and firecrackers at either the opposing group or the police before being dispersed, according to Vice News. Protesters from both sides were arrested.

"Where were you on New Year's Eve?" one protester yelled at the police, per CNN. "Why didn't you protect those women?"

Merkel seems to realize the New Year's Eve attack and subsequent fallout provides an almost unfathomable additional layer to what she has acknowledged is her administration's greatest challenge - Europe's mass influx of migrants and refugees.

She told reporters Saturday: "The events of New Year's Eve have dramatically exposed the challenge we're facing, revealing a new facet that we haven't yet seen."