The man in his 20s was previously suspected of eight assaults on women in Oslo and nearby Asker.
Now the suspicions are being expanded to include five more cases. Among the new victims is a woman in her 50s whom the man allegedly threatened in a forest in Bærum in April, Aftenposten writes.
The 13 crimes occurred between December and April, against women aged 26 to 93.
The man has been in custody for four weeks.
