A prosecutor in Norway has said that a far-right extremist who killed 77 people in 2011 still is "a very dangerous man" and therefore a poor candidate for release after 10 years in prison, as Norwegian law permits.

On the final day of a three-day parole hearing on Thursday, prosecutor Hulda Karlsdottir said in her closing argument that Anders Behring Breivik "has not shown any genuine remorse in court" and his behaviour there is part of a "PR stunt".

"In the clear view of the prosecution, Breivik's request for parole should not be granted," Karlsdottir said.

Breivik professed white supremacist views and flashed Nazi salutes on the hearing's opening day while claiming to have renounced violence.

A psychiatrist who has observed him since 2012 testified on Wednesday that Breivik cannot be trusted.

A prison official told the judges hearing the parole request "there is an imminent danger" that, if released, Breivik would again commit serious crimes.

Breivik is serving Norway's maximum 21-year sentence for setting off a bomb in Oslo's government district and carrying out a shooting massacre at a summer camp for left-wing youth activists.

He was declared criminally sane at his trial, although the prosecution argued that he was psychotic.

He did not appeal his sentence but unsuccessfully sued the government for human rights violations for denying him the right to communicate with sympathisers.

Although Norway's maximum prison sentence is 21 years, Breivik could be held longer under a provision that allows authorities to keep criminals in prison for as long as they're considered a menace to society.

The three-judge Telemark District Court is expected to rule on his parole request later this month.