Women hold up placards that read "Mrs. Merkel: Where are you? What are you saying? This worries us!" during a protest in front of the Cologne Cathedral, Germany, January 5, 2016. [Photo/Agencies]

BERLIN - German Chancellor Angela Merkel expressed her outrage over series of sex attacks committed against women in the western German city of Cologne on New Year's Eve, demanding a hard response from the law, her spokesman Steffen Seibert said on Tuesday.

Merkel spoke in the afternoon with Cologne Mayor Henriette Reker over the offenses which took place around Cologne's main train station on the New Year's Eve in a phone conversation.

"Everything must be done to find the perpetrators as quickly and comprehensively as possible and to punish them regardless of their origin or their background," said the statement.

In an interview with German media Tagesschau on Tuesday evening, German Interior Minister Thomas de Maiziere strongly criticized the work of the Cologne police on New Year's Eve, and also described the incidents in Cologne as "obnoxious, outrageous and unacceptable".

Meanwhile, he also stressed that there should be no general suspicion towards refugees.

On New Year's Eve, many women were surrounded, harassed, robbed, while one was raped in Cologne by around 1,000 men, who came "from the Arabic or North African region regarding their appearance", according to police.

By Tuesday evening, the number of criminal complaints filed has spiraled to more than 90. However, the police still have no leads about the perpetrators, said the city's police chief Wolfgang Albers in a press conference.