A brother of one of the victims of Norwegian mass killer Anders Behring Breivik threw a shoe at him in court, the first time the trial has been interrupted by a public outburst.

"Go to hell, go to hell, you killed my brother," the man screamed from the second row of the public gallery as he hurled the shoe at Mr Breivik a few metres away.

The shoe missed Mr Breivik but struck his co-defence lawyer, Vibeke Hein Baera, who was seated closest to the public gallery, during the presentation of an autopsy report.

Some in the courtroom applauded, or uttered the word "finally", and others started to cry.

The shoe thrower was removed by police. Police numbers were boosted in the court after the incident.

"If anyone wants to throw something, you can throw it at me when I'm entering or leaving the court," Mr Breivik was quoted by local media as saying after the incident.

"Don't throw things at my lawyers."

The incident came during a week of harrowing testimony from survivors of Mr Breivik's gun rampage across the small island of Utoeya last July, where the ruling Labour Party was holding a youth camp.

He killed 69 people there, many of them teenagers.

Mr Breivik has listened calmly to the descriptions of his killings and shown little emotion, except when hearing descriptions about how he was said to have let out "cries of joy" and laughed while shooting, which he has denied.

He has admitted the killings, but denies criminal responsibility. He says he was defending Norwegian ethnic purity from Muslim immigration and the multiculturalism backed by the Labour Party.

Mr Breivik has said he felt he had no choice but to strike back, bombing government offices in an attack that killed eight people and then carrying out the massacre at the Labour Party island summer camp.

During today's hearing, he said one person at Utoeya had attacked him during his rampage, throwing an object at his face, but gave no more details.

Ahead of the trial, one court-appointed team of psychiatrists concluded that Mr Breivik was psychotic, while a second found him mentally capable.

He has said he should either be executed or acquitted, calling the prospect of a prison sentence "pathetic" and an insanity ruling "worse than death".

If he is deemed sane, he could face a 21-year prison sentence with indefinite extensions for as long as he is considered dangerous.