The man who massacred 77 people in Norway's deadliest ever terror attack has won part of a lawsuit against the government for "inhuman treatment".


A court in Oslo ruled in Anders Breivik's favour on one of two claims for alleged human rights violations and rejected the other on Wednesday afternoon.


The right-wing extremist was convicted of terrorism and mass murder for 2011 bomb and gun attacks in Norway that killed 77 people. 


A summary of the ruling released by an Oslo district court said judges found his detention violated article three of the European Convention of Human Rights, which relates to "inhuman or degrading' punishment.The verdict 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."


Breivik's claim that authorities also violated article eight of the convention, which protects the respect for private and family life, including correspondence, was rejected.The court also ruled that the state will have to pay the prisoner's legal fees, totalling 331,000 Norwegian krone.