Anders Behring Breivik gives a far-right fist salute as he enters the court. (Reuters/ Fabrizio Bensch)

The trial of Anders Behring Breivik, who killed 77 people in bomb and gun attacks in Norway, has begun.

The right-wing fanatic has admitted his attacks on July 22, which began with a bomb blast in downtown Oslo, killing eight, and ended with a gun rampage at a Labour party youth camp on Utoya Island, in which he killed 69 more.

Breivik, 33, who smiled and gave a raised fist salute when he began his trial in an Oslo district court, does not accept legal culpability for the murders, which he claims were necessary to protect Norway from being taken over by Muslims.

Asked to address the court, Breivik said: "I do not accept your authority in this case. You have gotten your political mandate from forces that support multiculturalism."

His defence lawyer, Geir Lppestad, said that Breivik's outburst was not a formal complaint. Judge Wenche Behring said she would make a note of the general objection.

Breivik Trial: The Facts

The court will have to decide Breivik's sanity and therefore culpability for his crimes. Two assessments have been made of his mental state, one of which concluded that he was sane, another that he was insane.

Concerns have been raised that Breivik, who will testify for five days, will use the publicity of the trial to publicise his extreme views. He will be tried by a panel of five judges, three of whom are lay judges and two professionals.

Around 150 people are expected to testify in the trial, with more than 770 survivors and their families being represented by 162 lawyers.

Prior to the trial beginning, Breivik's lawyer warned that he will claim that his only regret with regard to his crimes is that he did not kill more people.

Norwegian newspaper VG rteported on a letter written by Breivik giving his plans for the trial.

"The court case looks like it will be a is an absolutely unique opportunity to explain the idea of [his manifesto] to the world."

In his manifesto, printed online and constituting around 1,500 pages, Breivik claimed that a trial offered a "stage to the world".

A majority vote of three of five judges will be required in the trial, with a verdict expected in mid-July.

Breivik is charged with terrorism and premeditated murder for a bombing in Oslo's government district, killing eight, and a shooting attack at a political youth camp, killing 69.

If convicted he would face a maximum sentence of 21 years in prison, though sentences can be extended if a criminal is considered a menace to society. If declared insane by the court, he would be committed to psychiatric care. Both sides can appeal the ruling to a higher court.

The trial continues.