The suspect in the Norway attacks, Anders Behring Breivik, will appear before a judge for the first time on Monday, but could still be weeks away from facing formal charges.
The author of twin attacks in and around Oslo that killed at least 93 people and wounded nearly 100 more will be brought to a central Oslo court-house for the first time since his arrest on Friday early evening.
"The suspect will appear on Monday before a court, where the judge will pronounce on his provisional detention," Oslo police commissioner Sveinung Sponheim told a news briefing.
The judge is first expected to rule on whether the hearing will be open to the public.
The judge will then decide on Behring Breivik's custody conditions while awaiting formal charges. Those charges will only be read out to the accused at a later hearing closer to actual trial.
Under Norwegian law, the authorities can keep a suspect under such provisional detention for a period of up to four weeks, which can be renewed.
Norwegian police said on Sunday that they still do not know the suspect's motives for the bombing and shooting spree targeting government offices in downtown Oslo and youth members of the country's governing Labour party.
Behring Breivik has acknowledged his actions, through his lawyer Geir Lippestad, but denies criminal responsibility. Lippestad said his client, who has published a vast revolutionary tract centred on an anti-Muslim "crusade," felt he had done "nothing reprehensible."