Norwegian mass murderer Anders Breivik won part of his human rights case against the Norwegian state.

The court upheld his claim that some of his treatment in captivity amounted to "inhuman or degrading treatment or punishment".

The right "represents a fundamental value in a democratic society" and also applied to "terrorists and killers," Judge Helen Andenaes Sekulic 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," judge Helen Andenaes Sekulic said in her ruling.

But his right to a private and family life had not been violated, she said.

The 37-year-old right-wing extremist was convicted of terrorism and mass murder in 2012 for bomb and gun attacks that killed 77 people the previous year.