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SKIEN, Norway — Mass murderer Anders Behring Breivik made a neo-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 did not speak.

Anders Behring Breivik enters a courtroom at Telemark prison in Skien, Norway, on Tuesday. LISE AASERUD / EPA

The 37-year-old right-wing extremist, who killed 77 people in a bomb and shooting rampage in 2011, sued the government last year, saying 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.

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The government is appealing against a surprise decision 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.

Judge Helen Andenaes Sekulic ruled that Breivik was wrongly kept in a "locked world" for 22-23 hours a day, even though it was comprised of a three-room cell with a training room, television and newspapers.

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.

A police uniform-clad Anders Breivik carries a handgun after planting a bomb in a car in a surveillance camera image captured in Oslo, Norway, on July 22, 2011. ABC Nyheter via SCANPIX NORWAY / Reuters, file

Breivik was convicted of mass murder and terrorism in 2012 and given a 21-year prison sentence that can be extended for as long as he's deemed dangerous to society. Legal experts say he will likely be locked up for life.

He is being held in isolation in a three-cell complex where he can play video games, watch TV and exercise. He has also complained about the quality of the prison food and having to eat with plastic utensils.

The government has rejected his complaints, saying he is treated humanely despite the severity of his crimes and that he must be separated from other inmates for safety reasons. Lawyers for the state will argue that the measures, including hundreds of strip searches, have been fully justified.

In recent months there has been some slight easing of Breivik's detention conditions. His lawyer has been allowed to talk to him from between bars rather than through a glass wall.

Breivik had carefully planned the attacks on July 22, 2011. He set off a car bomb outside the government headquarters in Oslo, killing eight people and wounding dozens. Dressed in a police uniform, Breivik then drove to the island of Utoya, about 25 miles away, where he opened fire on the annual summer camp of the left-wing Labor Party's youth wing. Sixty-nine people there were killed, most of them teenagers, before he surrendered to police.

At the time of the attacks, Breivik claimed to be the commander of a secret Christian military order plotting an anti-Muslim revolution in Europe, but now describes himself as a traditional neo-Nazi who prays to the Viking god Odin. He made a Nazi salute to journalists at the start of his human rights case last year.