An unrepentant Breivik, 33, gave the Oslo court a stiff-armed, clenched-fist salute before being handed the steepest possible penalty of 21 years.

His release can be put off indefinitely should he still pose a threat to a liberal society left traumatised by his bomb and shooting rampage last July.

The killer, who blasted a government building and gunned down dozens of teenagers at a summer camp, later claiming he was doing a service to a nation threatened by immigration, had said only acquittal or death would be worthy outcomes. His biggest concern was being declared insane – the only verdict he had said he would appeal.

Judge Wenche Elizabeth Arntzen dismissed a prosecution call for her to label Breivik mad, a ruling that would have seen him confined indefinitely to psychiatric care rather than prison.

Some survivors of the slaughter at the Labour party youth camp on Utoeya island had been keen to see Breivik held clearly responsible for his actions – and to avoid the insanity verdict that would have triggered lengthy and traumatic appeal hearings.

However, for many Norwegians the details were academic.

"He is getting what he deserves," said Alexandra Peltre, 18, whom Breivik shot in the thigh on Utoeya.

"This is karma striking back at him. I do not care if he is insane or not, as long as he gets the punishment that he deserves."

Breivik, who surrendered to police on the island without a fight, admitted blowing up the Oslo government headquarters with a fertiliser bomb, killing eight, on July 22, 2011, then shooting 69 people at the ruling party's summer youth camp.

Dressed in a black suit with a tie, Breivik smirked when he entered the courtroom and gave his now familiar far-right salute when his handcuffs were removed. He smiled again as the judge read out the verdict.

"He told me he will accept this verdict," his lawyer Geir Lippestad said, indicating there would be no appeal.

A lawyer for some victims and their families said they, too, were satisfied: "I am pleased, although that's not really the right word, and relieved. This is what we hoped for," said Mette Yvonne Larsen, who represented some of those affected in court.

"I have already received many messages from clients telling me this is justice served and they are happy it's over and will never have to see him again."

Breivik had described an insanity verdict as "a fate worse than death". Were he to have decided to appeal, the entire trial would have had to be repeated.

The killings shook the nation of five million, which had prided itself as a safe haven from much of the world's troubles, raising questions about the prevalence of far-right views in a country where oil wealth has attracted rising immigration.

Breivik justified his killing spree arguing that the centre-left Labour party was deliberately destroying the nation by encouraging Muslim immigration. His views, spread over the internet and aired during the trial, drew support from a few in Europe, but even most of the hardest right-wing fringe groups kept their distance from the self-confessed mass killer.

Although his victims were mostly teenagers, with some as young as 14, he rejected being called a child murderer, arguing that his victims were brainwashed "cultural Marxists" whose political activism would adulterate pure Norwegian blood.

"I stand by what I have done and I would still do it again," he said during his court testimony.