The move comes as police become increasingly confident that Behring Breivik acted alone, police prosecutor Christian Hatlo told AFP.
However, his release from solitary confinement on October 18th is basically a technicality, since the 32-year-old rightwing extremist will still remain isolated.
"He will not be allowed to receive mail or visitors and he will have no access to media," Hatol said.
"He will also be kept apart from other prisoners for his own safety," he added.
Police have had to ask Oslo's district court for an extension of the solitary confinement every four weeks since Behring Breivik's arrest on July 22nd.
The court decided that Behring Breivik, 32, will leave solitary confinement at the high-security Ila prison near Oslo next week, but he will remain in custody until at least November 14th, when a judge is expected to announce whether or not to extend his custody further.
He is expected to remain in preventive custody until his trial begins, probably during the first half of next year.
According to Hatlo, it is rare that solitary confinement — which Behring Breivik has called a form of "torture" — is enforced longer than 12 weeks.
On Monday, Behring Breivik will have been in solitary confinement for 12 weeks.
Police had wanted him kept apart for fear that he would be able to contact accomplices and tamper with evidence.
"For every day that passes we are increasingly sure" that he acted alone, Hatlo said.
"We have found nothing to suggest that accomplices exist even though we refuse to definitively rule out the possibility," he added.
At a custody hearing in Oslo's district court in August, Behring Breivik protested against his solitary confinement, calling it a form of "torture."
He has admitted setting off a car bomb outside the government offices in Oslo on July 22nd, killing eight people, before going on a shooting rampage on the nearby island of Utøya where the ruling Labour Party's youth wing was hosting a summer camp.
Sixty-nine people, mostly teens, died in the shooting massacre and police have said they found 186 empty shell casings strewn around the island.
In a manifesto he published on the internet just before the attacks, Behring Breivik said he was on a "crusade" against Islam and professed his hatred for Western-style democracy, saying it had spawned the multicultural society he loathed.