Norwegian prosecutors have formally charged Anders Behring Breivik 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 on Wednesday 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.
On July 22, Behring Breivik, who has claimed to be on a crusade against multi-culturalism and the "Muslim invasion'' of Europe, set off a car bomb outside government buildings in Oslo, killing eight people.
He then went to Utoeya island northwest of Oslo, and, dressed as a police officer, spent more than an hour methodically shooting and killing another 69 people, mainly teenagers, attending a summer camp hosted by the ruling Labour Party's youth wing.
The attacks will be viewed as two separate terrorist acts, according to Wednesday's indictment, which also showed that 56 of those killed on Utoeya were under the age of 20.
The document also showed that 67 of those killed on the island were shot to death, with at most eight bullets pulled from a single victim, while two had died from falls or drowning while trying to escape from Behring Breivik.
Thirty-three people had been shot but not died from their wounds, prosecutors said.
Trond Henry Blattmann, who himself lost a son in the massacre and who heads a support group for the victims' families, said hearing the charges against the confessed killer had been an emotional experience.
"The penalty handed to this man will never be enough in our eyes,'' he told AFP, adding though that it did not matter whether Behring Breivik was locked up in prison or an institution.
"The most important thing for us is, we hope, that he will never again set foot in Norwegian society,'' said Blattmann.
Behring Breivik is currently undergoing a second court-ordered psychiatric evaluation, after the initial one late last year found him criminally insane.
The diagnosis, which if supported by the court would rule out prison, sparked a wave of criticism, with many pointing to the years he spent planning the massacre and his calm demeanor as he executed his attacks.
But regardless of the findings of the second expert assessment of his criminal accountability, he will face trial and it will in the end be up to the judge to determine whether he can be sentenced to prison.
If found to be criminally responsible, the perpetrator of the worst massacre on Norwegian soil since World War II would face the maximum prison sentence in Norway of 21 years behind bars, or the same sentence with a provision allowing for an indefinite extension of his term until he is no longer deemed a danger to society.
On the other hand, if he is found to be not criminally responsible for his actions, he will be locked up in a closed psychiatric ward, possibly for life.