Crown Princess Mette-Marit's son, Marius Borg Høiby, 27, was reportedly arrested following an "incident in an apartment" in Frogner, Oslo on Sunday.
According to Se og Hør, Marius spent more than 30 hours in police custody before being released on Monday afternoon.
He allegedly attacked a woman in her 20s "psychologically and physically," the Norwegian newspaper reports.
She is said to have been admitted to a hospital where she was diagnosed with a concussion, and was discharged on Monday morning.
Marius was allegedly arrested some time after the incident at another address before being taken to a police station, where he was placed in "solitary confinement".
According to Se og Hør, he is now staying with his mother, Mette-Marit, 50, at her official residence, Skaugum, in Asker, just outside of Oslo.
The Crown Princess was scheduled to appear at the Paris 2024 Olympics with her husband, Crown Prince Haakon, on Tuesday but the future king attended the equestrian and athletics events alone.
A communications advisor at the Norway palace told HELLO!: "The Crown Princess has temporarily postponed her departure for the Olympics but hopes to travel later."
Marius is the firstborn son of Crown Princess Mette-Marit from her relationship with convicted felon Morten Borg.
He is not in line to the Norwegian throne and quit public life in 2017 to pursue studies in the US.
In an open letter published on the palace's website at the time, Mette-Marit said of her son, who was 20 at the time: "I was 23 years old and got a big responsibility. It has been the greatest gift in my life.
"Marius has always had a role that has been difficult to define in the public sphere. He is and will be an exceptionally important part of our family. Marius became a symbol of the unusual choice we made when we got married, at the same time he will not carry public duties like his siblings. He should not have a public role and is not a public figure.
"The role has also proved difficult to interpret for people around us in private. Ever since he was tiny. Everything from parents who have come with concerns and well-intentioned advice, to teachers who have always had different expectations of Marius's behaviour than that of others. And I'm no better myself. As a mother, I often find myself having expectations of Marius's behaviour that are unrealistic, and different from what I would have for his siblings."
Mette-Marit married Crown Prince Haakon at Oslo Cathedral on 25 August 2001 and the couple went on to welcome two children - future queen Princess Ingrid Alexandra and Prince Sverre Magnus.
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