Prosecutors in Norway have charged the son of Norway's crown princess with reckless behaviour and violating a restraining order a month after he went on trial for rape and dozens of other alleged offences.

Marius Borg Høiby was arrested the day before his trial began at the start of February, on suspicion of threats and violence against a woman in his flat in Oslo. Police remanded him in custody for the first four weeks of the trial.

Although allegations of bodily harm and knife threats have been dropped, prosecutors say the 29-year-old has admitted reckless behaviour and violating a restraining order.

He now faces a total of 40 charges and denies the most serious allegations.

Marius Borg Høiby is the son of Crown Princess Mette-Marit and grew up in the royal family, but he is not a member of Norway's royal house. He was four when his mother married Crown-Prince Haakon in 2001.