Flowers and posters are placed in the square between the city cathedral and the railway station in Cologne, Germany, January 11, 2016, where the vast majority of dozens of New Year Eve assaults on women took place. REUTERS/Wolfgang Rattay

BERLIN (Reuters) - German prosecutors have offered a cash reward of 10,000 euros ($10,890) for information that could lead to the arrest of suspects in mass sexual assaults on women partying on New Year’s Eve in the city of Cologne.

More than 600 women in several cities across Germany filed complaints ranging from sexual molestation to theft in attacks on the New Year’s weekend and police investigations are focused on illegal migrants from North Africa as well as asylum-seekers.

The incidents deepened public doubts about Chancellor Angela Merkel’s decision to open Germany’s doors to refugees and migrants, whose numbers reached 1.1 million last year.

The prosecutor’s office in Cologne said on Thursday more details about the reward for helping find suspects would be communicated by the police this week.

German police said they had so far been able to identify 32 people suspected of roles in the violence in Cologne, including 22 who were planning to seek asylum in Germany.

But identifying perpetrators has been a challenge for police, who have been smarting from criticism that they failed to stop the attacks. The Cologne police chief has been sacked over the matter.

The assaults shocked Germans and prompted politicians to introduce harsher penalties against offending asylum seekers and foreigners.