Norwegian mass murderer Anders Behring Breivik made a Nazi salute as he walked into a courtroom at a high-security prison where judges on Tuesday began reviewing a ruling that his solitary confinement is inhumane.

Dressed in a dark suit, the bearded Breivik stared briefly at reporters while making the salute but didn't speak.

Judge Oystein Hermansen asked him not to repeat the salute, saying it insulted the dignity of the court.

"It also disturbs what we are dealing with here," Hermansen said, brushing aside attempts by Breivik to defend his action.

The 37-year-old right-wing extremist, who killed 77 people in a bomb and shooting rampage in 2011, sued the government last year. He argued that his solitary confinement, frequent strip searches and the fact that he was often handcuffed during the early part of his incarceration violated his human rights.

But lawyers representing the government said that he enjoys better prison conditions than some inmates in Norway. They also warned that he remains a threat and should continue to be held in solitary confinement.

The government is appealing a surprise decision in April by the Oslo District Court, which sided with Breivik's claims that his isolation in the maximum-security Skien prison breaches the European Convention on Human Rights.

The ruling said "the prohibition of inhuman and degrading treatment represents a fundamental value in a democratic society. This applies no matter what — also in the treatment of terrorists and killers." It also ordered the government to pay Breivik's legal costs of 331,000 kroner ($41,000).

However, it dismissed his claim that his right to respect for private and family life was violated by restrictions on contacts with other right-wing extremists.