An expert team monitoring the Norwegian killer, Anders Behring Breivik, in prison said they believed he was not insane, disagreeing with the original conclusion by court-appointed psychiatrists, the BBC has said.

Breivik, who has been jailed after admitting to killing 77 people in Norway last summer, has faced indefinite detention in a psychiatric hospital as a mental evaluation in November last year declared him legally insane.

In their report based on conclusions made after 13 interviews with Breivik, two court-appointed psychiatrists said the 32 year-old lived in his “own delusional universe where all his thoughts and acts are guided by his delusions.”

But the conclusion has been challenged by the team of four psychiatrists assessing Breivik in jail. In a report submitted to the court by Public Prosecutor Svein Holden, the experts said they did not believe Breivik was psychotic or schizophrenic and did not think he needed drugs, the BBC said.

The court is expected to decide within the next few weeks whether or not to order a new psychiatric expertise, the BBC report said.

Breivik has confessed to killing eight people with a car bomb in downtown Oslo on July 22, 2011, and then gunning down 69 others on the island of Utoya, which was hosting a summer camp for the governing Labor Party's youth branch. He is due to go on trial on terrorism charges on 16 April, regardless of whether or not he is regarded as sane.