The judge will decide whether to keep the session closed, prosecutors said in an email in English. "This issue will be negotiated after the opening of the meeting (hearing)," they said. "The judge will then read his decision to the press."
Prosecutors want Breivik detained for an initial eight weeks -- normally this is in solitary confinement with no access to news, letters or visitors, except a lawyer. His custody can be extended before his trial on terrorism charges.
Police have said a trial could be a year away. The maximum jail term in Norway is 21 years, although that can be extended if there is a risk of repeat offences.
"In theory he can be in jail for the rest of his life," said professor of criminal law at the University of Oslo, Staale Eskeland.
Breivik, a self-confessed mass killer, has said through his lawyer that he wants to explain his motives at the hearing.
The 32-year-old, who portrays himself as crusader against a tide of Islam in a rambling 1,500-page online manifesto, says he wants to explain acts he deemed 'atrocious' but 'necessary'.
The hearing, expected to start after 1 p.m. (1100 GMT), has generated a debate about freedom of expression, with many Norwegians opposed to allowing a man who has shaken the nation's psyche to expound his radical views.
More than 60,000 people have signed up to a Facebook page called "Shut the doors on Monday," calling on the court to deny Breivik the publicity he craves.
Another Facebook group called "Boycott Anders Behring Breivik" carried the message: "He has planned this stage, to get propaganda. Do NOT let him get that freedom...Boycott all media describing the Norwegian terrorist and his beliefs."
Breivik has asked to wear a uniform in court, but his lawyer, Geir Lippestad, said he did not know what type. The killer was dressed as a policeman during his shooting spree.
Breivik has not served in the armed forces but in some of the pictures he posted on the Internet before his killing spree he was dressed in a military-style outfit.
Lippestad said his client had admitted to Friday's shootings at a Labour youth camp and an earlier bombing that killed seven people in Oslo's government district, but that he denies any criminal guilt.
"He has been politically active and found out himself that he did not succeed with usual political tools and so resorted to violence," Lippestad told TV2 news.
"I await a medical assessment of him," he said.
SAVING EUROPE
The worst peacetime massacre in the normally placid country's modern history appears to have been driven by Breivik's mission to save Europe from what he sees as the threats of Islam, immigration and multi-culturalism.
That he surrendered to police when finally confronted on the tiny island of Utoeya after shooting dead 86 youngsters underlines his desire to secure a public platform.
Breivik wrote in his manifesto, posted hours before his attacks, that if he survived his assault and was arrested, this would "mark the initiation of the propaganda phase."
Norwegian newspapers focused on the victims as shock turns to mourning, giving chilling new accounts of the island massacre and focusing on acts of bravery which saved lives.
The main broadsheet Aftenposten led with "Sorrow unites Norway" and printed a picture of a central Oslo square filled with flowers and lit candles in remembrance of the dead.
Daily Dagsavisen asked "Why didn't you come earlier?" citing screams by youth as police arrived on Utoeya island on Friday -- an hour after they were notified of the shooting.
Norway will observe a minute of silence at midday.
"He explains himself fairly calmly, but every now and then expresses emotion," Lippestad said of Breivik. "He buries his head in his hands."
"He has said that he believed the actions were atrocious, but that in his head they were necessary," adding his client did not feel he deserved punishment.
Police believe Breivik acted alone after losing faith in mainstream parties, even those that have gained popularity and parliamentary seats on anti-immigration policies in otherwise liberal, tolerant European nations, including affluent Norway.
IMMIGRATION
The attack was likely to tone down the immigration debate ahead of September local elections, analysts said, as parties try to distance themselves from Breivik's beliefs and reinforce Norwegians' self-image as an open, peaceful people.
Norway's immigrant numbers nearly tripled between 1995 and 2010 to almost half a million in a population of 4.8 million.
The sense that many were drawn by Norway's generous welfare handouts helped spur the growth of the Progress Party which became Norway's second biggest in parliament after the 2009 election on a largely anti-immigration platform.
Breivik was once a member of the party, but left complaining it was too politically correct. It was then he began scheming to "resist," burying ammunition more than a year ago, weight-lifting, storing up credit cards and researching bomb-making while playing online war games.
After three months of laboriously pounding and mixing fertilizer, aspirin and other chemicals on a remote farm, Breivik drove a hire car packed with the results to the center of Oslo on Friday, triggering the device outside government offices, killing seven and shattering thousands of windows.
He then drove to the small island of Utoeya, 45 km (28 miles) away. Dressed as a policeman, he calmly shot down youngsters at a youth summer camp of the ruling Labour Party. His terrified victims tried to hide under beds or in the woods. Some leapt into the lake and tried to swim to the mainland.
"This is going to be an all-or-nothing scenario," Breivik wrote in his English-language online journal on the morning of the attack. "First coming costume party this autumn, dress up as a police officer. Arrive with insignias:-) Will be awesome as people will be very astonished:-)."
"DUM-DUM"
A surgeon at a hospital that treated 35 of the wounded said Breivik may have used "dum-dum" bullets for maximum damage.
"These bullets don't explode inside the body but fragment into pieces more quickly than other bullets," Colin Poole, chief surgeon of the Ringerike district hospital, told Reuters.
While Breivik was stalking his prey on Utoeya, it took police a full hour to get a team of elite forces to the island after one boat, overloaded with officers and equipment, was forced to stop when it began to take on water.
Norwegian television managed to charter a helicopter and filmed the killer before the police showed up. When the armed team did arrive, Br eivik gave himself up without a fight.
"He had at that point used two weapons and had been, and was still, in possession of a substantial amount of ammunition," Johan Fredriksen, chief of staff at Oslo police. "Thus, the police's response has hindered further killing on the island."
