The 27-year-old son of Norwegian Crown Princess Mette-Marit was arrested at the weekend on suspicion of assaulting a woman, police said on Wednesday.

Mette-Marit's son Marius Borg Hoiby was born in 1997 from a relationship prior to her 2001 marriage to Crown Prince Haakon, the heir apparent to the Norwegian throne.

Police said they were called to an Oslo address early Sunday after an overnight altercation in an apartment.

A man in his 20s was arrested over the incident and released from custody the following day, police said in a statement.

"As it has been made known in several media that this (person) is Marius Borg Hoiby, the police confirm that it is Hoiby who is a suspect in the case." 

Police said he was suspected of causing "bodily harm and damage". They did not identify the woman, saying only there was "relationship between the accused and the victim".

Police said they had "no information that the victim suffered serious injuries".

Crown Prince Haakon, currently in Paris for the Olympics, on Wednesday told Norwegian media in the French capital it was a "serious" matter.

"It's a serious matter when police are involved like this," TV2 quoted him as saying on its website.

"At the same time, it would not be right for me to comment on it at this time." 

While Hoiby was raised by Mette-Marit and Haakon together with his step-siblings, 20-year-old Princess Ingrid Alexandra and 18-year-old Prince Sverre Magnus, unlike them he has no official public role.