An appeals court in Norway is considering whether the prison conditions under which mass murderer Anders Behring Breivik is being held amount to a violation of his human rights.

The six-day trial ended Wednesday in a makeshift courtroom inside Skien prison in southern Norway where Breivik, 37, is serving a 21-year sentence for killing 77 people in a 2011 bomb-and-shooting rampage.

Breivik's lawyer, Oystein Storrvik, spent most of the last day seeking to show that restrictions on his client's visitors and the strict control over Breivik's mail and phone calls have led to a lack of human interaction and privacy, which amounts to a violation of his rights.

The case is "really about a person that is sitting very, very alone in a small prison within a prison" since 2012, explained Storrvik.

He dismissed the benefits of the weekly visits by a state-appointed prison confidante for Breivik, saying "it's a paid job."

Addressing the court last week, Breivik said his solitary confinement had deeply damaged him and made him even more radical in his neo-Nazi beliefs.

The Norwegian state rejected the criticism and said efforts to find a prison confidante show the authorities have "gone out of their way" to remedy the situation.

In a surprise verdict last year, the Oslo District Court sided with Breivik, finding that his isolation was "inhuman (and) degrading" and breached the European Convention on Human Rights. It ordered the government to pay his legal costs.