Asylum seekers could be deported if they are found to have taken part in a string of New Year sex attacks in Cologne, Germany's justice minister has said.

Police said witnesses have described the perpetrators as being of "Arab or North African origin", but there is little solid information on who committed the assaults.

That has been seized upon by some opponents of Germany's welcoming stance towards those fleeing conflict.

Officials have warned against casting suspicion on refugees in general.

Nevertheless, Justice Minister Heiko Maas said in an interview with the Funke newspaper group published on Thursday that "deportations would certainly be conceivable".

He said the law allows for people to be deported during asylum proceedings if they are sentenced to a year or more in prison, and that is possible with sexual offences.

At least 106 women have come forward to file criminal complaints of sexual assault and robbery during the New Year's Eve festivities, authorities say, including two accounts of rape.

Interior Minister Thomas de Maiziere said on Wednesday that "anyone who commits serious crimes, whatever status he is in, must reckon with being deported from Germany".

"If it turns out that refugees were the perpetrators, then they forfeited their right to be guests," Andreas Scheuer, the general secretary of the conservative Christian Social Union - the smallest party in Chancellor Angela Merkel's coalition government - was quoted as telling the daily Bild.