MASS murderer Anders Behring Breivik, who killed 77 people in a bombing and shooting rampage in 2011, is set to return to court tomorrow as the government appeals against a ruling that his isolation in prison breaches the European Convention on Human Rights. The case, scheduled to last six days, will be heard in a makeshift courtroom in the gym of Skien prison in southern Norway, where Breivik is incarcerated.

The 37-year-old terrorist – who admitted to the killings which prime minister Erna Solberg called “one of the darkest days in Norwegian history” – was convicted in 2012.

He was handed a 21-year prison sentence that can be extended for as long as he is deemed dangerous to society. Legal experts have since stated that the right-wing extremist is likely to be locked up for life.

Breivik has often complained about his treatment and prison conditions. Indeed last year, he sued the government, complaining 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.

He is held in isolation in a three-cell complex where he can play video games, watch television and exercise.

The Norwegian has also complained about the quality of the prison food, the requirement of eating with plastic utensils and the fact that he is not able to communicate with sympathisers.

The government has rejected his complaints, stating that he is treated humanely despite the severity of his crimes. Officials say that he must be separated from other inmates for safety reasons.

However, in a surprise ruling in April, the Oslo District Court 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.”

The court also ordered the government to pay Breivik’s legal costs of £31,786. But it dismissed Breivik’s claim that his right to respect for private and family life was violated by restrictions on contacts with other right-wing extremists.

Breivik planned the 2011 attacks meticulously, setting off a car bomb outside the government headquarters in Oslo, killing eight people and wounding dozens.

He then drove to the island of Utoya, some 25 miles away, where he opened fire on the annual summer camp of the Labour party’s youth wing. Sixty-nine people were killed there, most of them teenagers, before Breivik 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 investigators found no trace of the group.

He 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.

Breivik’s lawyer, Oystein Storrvik, said his client was satisfied with last year’s verdict and that prison authorities would have to lift some of his restrictions.

However, many Norwegians feel Breivik has already had too much attention. Mette Yvonne Larsen, a lawyer who represented Breivik’s victims and their families, says her official line is “not to comment because we don’t want to give him [Breivik] any visibility.”