German police have identified 31 people, including 18 asylum seekers, suspected of playing a role in mass sexual assaults, robberies and violent attacks committed in Cologne on New Year's Eve.

Interior Ministry spokesman Tobias Plate told reporters that "Of the 31 suspects whose names are known, 18 have asylum seeker status."

Nine of those suspected of involvement in the attacks are Algerian, eight are Moroccan, five Iranian, four Syrian, two German, an Iraqi, a Serb and a US citizen.

Plate said that the suspects' alleged offences were "mostly theft and causing bodily harm".

Welt am Sonntag citing police officers on duty on the night of the attacks said that the identity of 100 people acting suspiciously had been checked, with 71 identified and 11 remanded in custody.

Police have recorded 170 alleged crimes committed by a group of men outside Cologne's central station. Among them are 117 allegations of sexual assault and two of rape.

Police have arrested two men, aged 16 and 23, of North African origin, in connection with the attacks. Videos showing violent attacks and sexual assaults committed outside the station were found in the men's possession, as well as notes containing translation of phrases including "nice breasts", "I want to kill you" and "I want to have sex with you" from Arabic to German, Germany's WDR reported.

German Chancellor Angela Merkel has called for those foreigners found guilty of the crimes to be deported. She said "clear signals" had to be sent to those not prepared to abide by German laws.

Legislation drafted by Merkel's CDU calls for those sentenced to prison or probation to be made ineligible for asylum.