Mass-killer Anders Breivik believed he was part of a secret organisation dedicated to removing Islam from Europe, the prosecution announced on Monday at the start of his trial.
Prosecutor Svein Holden's opening statement focused on Breivik's early life and how they believe he came to hold his beliefs.
Holden said he claimed to be part of a secret organisation modelled on the medieval Christian military order the Knights Templar, aimed at fighting Islam, as detailed in the manifesto Breivik wrote, which came to light following the attacks. But the prosecutor said that in their opinion "no such network exists".
"There is one subject, in particular that stands out," he said. "Namely that Breivik claims he became a member of the Knights Templar in London at a meeting in April 2002."
Police have not been able to substantiate Breivik’s claims of being in a group, and believe he acted alone.
The 33-year-old made a far-right salute as he arrived at a courtroom to face trial over the murders of 77 people in Norway last year, and interrupted proceedings to say that he does not recognise the authority of the Norwegian court.
He told judges he acknowledged killing 77 people in twin attacks in Oslo and at a Labour Party youth camp on the islands of Utoya, but pleaded not guilty, saying he was acting in "self-defence."
As some left while the prosecutor showed the "effects of the explosion" in Oslo, Breivik smirked and appeared to be holding back his laughter.
The prosecutor outlined before the footage was shown the images, which were not broadcast to cameras, that many in court had expressed their wish to leave the court while the video played.
"As the chair of the court initially stated I have been notified that there are several affected parties who do not wish to see the opening part of this particular statement," prosecutor Holden said.
The prosecutor then outlined the details of Breivik's shooting spree on Utoya island and a Labour party summer camp, before playing an audio recording of his time on the island.
The court was played audio where the killer said he wished to "surrender", around 40 minutes after he arrived on the Island. They also heard footage of a girl sobbing on the phone to police, saying: “I can hear the shots. I’m in the toilet, I’ve locked myself in a booth. There’s someone shooting, walking around shooting. Yes, there’s silence, he’s just outside. He’s coming, he’s coming. Quickly.”
The prosecution detailed how Breivik sold fake diplomas on the Internet and played the computer game World of Warcraft "extensively" in 2006.
He only showed emotion when the court was played a 12-minute propaganda film, Knights Templar 2083, which brought tears to his eyes.
The lawyer for Breivik's defence Geir Lippestad said the court would hear oral and written evidence from the killer, saying it would be crucial "for the court to decide on an independent basis whether he is legally sane and can be punished or not."
He said Breivik wished to be sentenced as a sane person, stressing: "The defendant's wish is to be sentenced as a legally sane person. So our evidence will support that claim."
Breivik told judge Wenche Elisabeth Arntzen: "I do not recognise the Norwegian courts. You have received your mandate from political parties, which support multiculturalism. I do not acknowledge the authority of the court."
Breivik stood up again to confirm his date of birth and that he was currently in prison. The judge said: "And you are unemployed?"
The self-confessed killer showed no emotion as the judge read out the names and details of the people he killed in the shooting spree, the youngest of whom was just 14-years-old.
Wearing a dark suit and metallic-coloured tie, he looked down and touched his chin as the gruesome details of their deaths were read out.
He told the judge: "I do not recognise the Norwegian courts"
Some of the details of the murders and injuries were so horrific the Norwegian media bleeped them out.
Overall 102 names, dates of births and details of those killed and injured were read out in court over 30 minutes.
After hearing the charges, Breivik said it was "self defence", telling the judge: "I acknowledge the acts but I do not plead guilty, I claim that I was doing it in self defence."
One of the survivors of the massacre, Jorid Nordmelan, who will hear Breivik testify, said the trial was unprecedented.
"It's a historical date for Norwegians," she told the BBC. "We never had a trial like this, so we don't know what's going to happen.
Armed police walk in the street outside the Oslo district courtroom
"Prosecutors told me they were going to make the opening statements awful, so that people can just feel what he did right there."
Since Breivik has confessed to the July 22 attacks - claiming they were necessary to protect Norway from being taken over by Muslims - the key issue that remains unresolved is his mental health. The trial is likely to focus on whether or not the killer is insane, after contradictory psychiatric reports.