BERLIN (AFP) - Thirty-one suspects, including 18 asylum seekers, are under investigation for offences including assault and theft in Cologne on New Year's Eve with the perpetrators of sexual assaults yet to be identified, Germany's interior ministry said on Friday.

"Of the 31 suspects whose names are known, 18 have asylum seeker status," said ministry spokesman Tobias Plate, citing federal police figures and indicating that their alleged offences were "mostly theft and causing bodily harm".

Federal police had recorded several complaints about sexual offences, but "the perpetrators for these have not been identified," he said.

The suspects include nine Algerians, eight Moroccans, four Syrians, five Iranians, one each from Iraq, Serbia and the United States, and two Germans, he said.

Cologne's state police have separately confirmed recording some 121 complaints of assaults, ranging from two alleged rapes to several accounts of groping, in what were apparently coordinated attacks in a large crowd of revellers during year-end festivities.

Victims blamed men of "Arab or North African" appearance, inflaming a heated public debate about Germany's ability to integrate the nearly 1.1 million asylum seekers the country took in last year.