Norway has defended the prison conditions under which mass murderer Anders Behring Breivik is being held.

State attorney Fredrik Sejersted presented his closing statement on Tuesday in an appeals trial against a lower court ruling that found Breivik's isolation in prison violated his human rights.

The "state is allowed to defend itself", Mr Sejersted said at the end of a day-long session where he sought to prove that Breivik was being treated in line with democratic principles.

"The Norwegian Constitutional state has responded in a way that is worthy of this state," he said, adding that he shook Breivik's hand on the first day of the trial because "that is what we do in Norwegian courts".

During the trial, the state sought to show that Breivik does have meaningful human contact on a daily basis, including a weekly meeting with a priest with whom he can have confidential conversations.

"There can be no doubt that Anders Behring Breivik is very much being treated humanely" and that restrictions to limit his interactions with other right-wing extremists were necessary, Mr Sejersted said.

The hearing was taking place at the high-security prison in southern Norway where Breivik, a right-wing extremist, is serving a 21-year sentence for killing 77 people in a 2011 bomb-and-shooting rampage.

Breivik, 37, told the court last week that his solitary confinement in prison has deeply damaged him and made him even more radical in his neo-Nazi beliefs.

The hearing by the Borgarting Court of Appeals is taking place in a makeshift courtroom in the gym at the prison in Skien, 135 kilometres (85 miles) south-west of the capital, Oslo.

It ends on Wednesday, with a ruling expected in February.