Updated at 12:25 p.m. ET: Militant Anders Behring Breivik admitted he killed 77 people in a massacre last July, but said he was pleading not guilty on the first day of a trial that threatens to turn into a "circus" showcasing his anti-Islamic views.

As he arrived in court - the early part of the session was broadcast on television - Breivik gave a salute, raising his arm with his fist clenched.

The 33-year-old said: "I do not recognize the Norwegian courts. You have received your mandate from political parties which support multiculturalism. I do not acknowledge the authority of the court."

The trial will turn on whether Breivik is found guilty or insane.  If sane, he faces up to 21 years in prison; if deemed criminally insane, he would be committed to psychiatric care.

Shed tears
Listening impassively for hours as prosecutors read out an indictment detailing how he massacred teenagers trapped on a island resort outside Oslo, he only shed tears when the court later showed one of his propaganda videos.

Fabrizio Bensch / Reuters

Anders Behring Breivik raises his fist as he arrives to courtroom for the first day of his trial in Oslo, Monday.

"I acknowledge the acts but not criminal guilt as I claim self defence," he added, seated in front of a bullet-proof glass wall.

Occasionally suppressing a yawn, cracking his knuckles and sipping water, he stared down at the indictment papers, following without visible emotion the list of his killings as the prosecutor read out each one. Some details were so graphic that Norwegian television bleeped out descriptions of the massacres.

Breivik shot most of his victims several times, often using the first shot to take down his target then following up with a shot to the head. His youngest victim was 14. He later surrendered as "commander of the Norwegian resistance movement".

Prosecutors played a recording of an emergency call made by one of the summer campers hiding in the bathroom of a cafe.

"There's shooting all the time, I've seen many injured. He's inside!" Renate Taarnes screamed, as 13 people in the cafe were shot dead. "He's coming ... he's coming," she said as shots could be heard in the background.

But Breivik only became tearful while watching a movie of still pictures accompanied by text of his vision of evils of "multiculturalism" and "Islamic demographic warfare".

"I think he feels sorry for himself," said Mette Yvonne Larsen, one of the lawyers representing victims. "His project didn't work out, that's why he's crying. He's not crying for the victims ... he's crying over his extremely childish film."

Heiko Junge / Pool via AFP - Getty Images

Rightwing extremist Anders Behring Breivik sheds a tear during his trial in Oslo courthouse as the court views a propaganda film he made.

The trial is scheduled to last 10 weeks and has raised fears that it could reopen wounds in Norway, a country that sees itself as a tolerant and peaceful society.

PhotoBlog: Anders Breivik in court

The "lone wolf" killer intends to say he was defending Norway against multiculturalism and Islam. He says his attacks were intended to punish "traitors" whose pro-immigration policies were adulterating Norwegian blood.

More than 200 people sat in the specially built courtroom while about 700 attack survivors and family members of victims watched on closed-circuit video around the country.

"It will be a tough time for many," survivor Vegard Groeslie Wennesland, 28, said outside the courtroom. "Last time I saw him in person he was shooting my friends."

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Last July 22, Breivek set off a bomb in the centre of Oslo before heading to the youth camp on Utoeya, an island in a lake 25 miles outside the capital, gunning down his victims while police took more than an hour to get to the massacre site in the chaos that followed the bomb blast.

Disguised as a police officer, Breivik managed to lure some of his victims out of hiding, saying help had arrived. Other victims jumped into the lake, where he shot them in the water.

Prosecutor Inga Bejer Engh spoke of the "panic and mortal fear in children, youths and adults" trapped on the island.

While video footage of the Oslo bomb blast was played to the court, victims and their families cried as but Breivik smiled on several occasions.

Prosecutors painted an image of a Breivik obsessed with the "World of Warcraft" computer game, prompting the judge to ask whether the game was violent. Breivik broke into a smile when the image of his online character was displayed.

An initial psychiatric evaluation concluded that Breivik was criminally insane while a second, completed in the past week, found no evidence of psychosis. Resolving this conflict could be the five-judge panel's major decision.

If found guilty and sane, Breivik faces a maximum 21-year sentence but could be held indefinitely if he is considered a continuing danger. If declared insane, he would be held in a psychiatric institution indefinitely with periodic reviews.

Meanwhile he has made clear he intends to make use of the trial to air his views when he testifies next week.

 "Your arrest will mark the initiation of the propaganda phase," he wrote in a manual for future attackers, part of a 1,500-page manifesto he posted online, according to Reuters. "Your trial offers you a stage to the world."

In a recent letter seen by Norwegian newspaper VG, Breivik added: "The court case looks like it will be a circus ... it is an absolutely unique opportunity to explain the idea of (the manifesto) to the world."

Reuters and The Associated Press contributed to this report.