The Norwegian man who admitted gunning down 69 young adults attending a leadership camp and eight others in a bombing attack has cried out torture over his solitary confinement at a court hearing on Monday.

After a judge ordered that he remains in isolation for another four weeks, mass killer Anders Behring Breivik told the court hearing his case that keeping him in solitary confinement in prison was a form of "torture."

Under Norwegian law, solitary confinement can only be imposed for four weeks at a time, but extensions are allowable towards the end of the fourth week.

Breivik admitted to the killings on July 22, and he has been kept in isolation for two months.

Judge Anne Margrethe Lund said the isolation was a necessary move to keep Breivik from establishing communication with possible allies outside jail. Police are still investigating whether Breivik has a network that helped him carry out the killings.

In a news conference, Lund said Breivik tried to raise irrelevant issues to her court.

"He wanted to communicate something to the court, but that wasn't relevant to the decision the court was to make today, so therefore he was not allowed to explain further regarding that issue," Lund explained.

Breivik's lawyer Geir Lippestad told reporters Breivik showed no signs of remorse for the killings.

"He has not expressed any remorse," Lippestad said. "He appeared calm and restrained as he had been earlier," adding that Breivik finds his isolation unbearable.

"He said it is tough to be in isolation," Lippestad said.