Norwegian prosecutors formally charged Anders Behring Breivik yesterday with committing acts of terror when he killed 77 people last July, but said he would likely be sentenced to psychiatric care instead of prison.

The 33-year-old right-wing extremist “has committed extremely serious offences on a scale that has never previously been experienced in our country in modern times,” the 19-page indictment read.

The charges carry a penalty of up to 21 years in prison, although a provision may enable the term to be extended for as long as he is considered a danger to society.

The prosecution meanwhile said it at this stage planned to pursue the case on the premise that Behring Breivik was criminally insane and therefore not responsible for his acts, and as such would call for him to be sentenced to confinement in a psychiatric ward.

But it reserved the right to alter that view if new elements emerged about his mental health by the end of the trial.

“There will have to be very significant new elements” for us to call for prison instead of psychiatric care, Inga Bejer Engh, one of two prosecutors in charge of the case, told AFP.

Police read the charges to Behring Breivik yesterday morning at the high security Ila prison outside Oslo where he is being held pending the beginning of his trial on April 16.

Afterwards, police officer Tore Jo Nilsen told reporters gathered outside the prison that the confessed killer had been “completely calm” during the 30 minutes it took to read the charges.

Behring Breivik’s main defence attorney Geir Lippestad said his client was disappointed the prosecutors were not initially requesting a prison sentence.

He “himself thinks he is criminally responsible and is disappointed that the prosecution has said it will call for mandatory psychiatric care,” he told commercial broadcaster TV2.