A son of Norway's crown princess has been charged with 32 offences including four rapes and several acts of violence and assault, a prosecutor said on Monday.

Marius Borg Hoiby, who was born from a relationship before Crown Princess Mette-Marit's married Crown Prince Haakon, has been under investigation since his arrest on 4 August last year on suspicion of assaulting a girlfriend.

In addition to four counts of rape, the charges include domestic abuse against a former partner and several counts of violence, disturbing the peace, vandalism and violation of restraining orders against another former partner.

He is also charged with filming the genitals of a number of women without their knowledge or consent, public prosecutor Sturla Henriksbo told reporters.

"The maximum penalty for the offences listed in the indictment is imprisonment of up to 10 years," he said.

"These are very serious acts that can leave lasting scars and destroy lives," the prosecutor said.

"The fact that Marius Borg Hoiby is a member of the royal family should, of course, not mean that he should be treated more lightly or more severely than if similar acts had been committed by others," Henriksbo stressed.

The four rapes for which Hoiby is charged allegedly took place in 2018, 2023 and 2024, the last one after the police investigation began.

Hoiby has already admitted to assault and vandalism in the August 2024 incident for which he was arrested.

In a public statement 10 days after his arrest, he said he had acted "under the influence of alcohol and cocaine after an argument", having suffered from "mental troubles" and struggling "for a long time with substance abuse".

Hoiby was propelled into the spotlight at the age of four when his mother married Norway's crown prince, with whom she went on to have two more children.

He was raised by the royal couple alongside his step-siblings Princess Ingrid Alexandra and Prince Sverre Magnus, aged 21 and 19.

Unlike them, however, he has no official public role.