Prosecutors in Cologne said Thursday they are offering a reward of 10,000 euros ($10,920) for information leading to the arrest or identification of those who committed sexual assaults and robberies during New Year's.

A spokesman for Cologne prosecutors said they have so far received 652 criminal complaints from that night, when groups of drunken men described as being mostly of "Arab or North African" origin attacked revelers at the city's main train station.

At least 331 complaints alleged sexual assaults, including two cases of rape, Ulrich Bremer told The Associated Press. In total, 739 victims have come forward — mostly women — of whom 430 alleged they had been sexually assaulted in some way.

Bremer said authorities have evaluated 350 hours of video and interviewed 120 witnesses. Police are calling for anyone who has more video or photographs of the scene that night to upload it to their website.

The scale and nature of the attacks has triggered a nationwide debate in Germany about the country's ability to integrate refugees, because some of the suspects are asylum seekers.

Bremer said authorities have charged 13 men with robbery, theft, dealing in stolen goods and resisting arrest. Five men are in custody, he said. The number of people charged is likely to rise in the coming days as police forward their findings to prosecutors, Bremer added.

The governor of North Rhine-Westphalia state, where Cologne is located, expressed regret for the attacks.

Hannelore Kraft told the state parliament that she understood how the incident made citizens feel insecure, but insisted that it shouldn't be used to tarnish the vast majority of innocent refugees. Germany saw almost 1.1 million asylum seekers arrive last year, many of them from war-torn Syria.

"After Cologne, we need more, not less, integration," Kraft said, adding that her state would continue to welcome those fleeing war and persecution elsewhere in the world.

Asylum seekers from countries such as Algeria and Morocco, who stand little chance of having their request approved, should be processed more swiftly, she said.