The suspect charged with carrying out a massacre at a youth camp in Norway and a bombing in the capital, Oslo, says he acted alone, police say.
Anders Behring Breivik, 32, admitted to carrying out both attacks, which he described as "gruesome but necessary".
At least 93 people were killed in Friday's attacks - 96 have been injured and some are still missing.
He is set to appear in court on Monday but it is not clear if the session will be open or closed to the public.
Mr Breivik has said he will explain his actions in court, but a judge will decide whether the hearing is to be opened up.
Memorial services have been held across the country, including at the main Lutheran cathedral in Oslo.
Norway's King Harald V and his wife Queen Sonja attended the service, along with Prime Minister Jens Stoltenberg, laying single white flowers outside as they entered.
The pews in the church were full, with the congregation spilling into the square outside, which was covered in candles and flowers.
Mr Stoltenberg told the mourners that the two days since the attacks took place felt like "an eternity - hours, days, and nights filled with shock and angst and crying".
As many of those in the cathedral wept, he said: "Each and every one of those who've left us is a tragedy - together, it's a national tragedy."
Throughout the day people continued to pour into the square outside the cathedral, laying flowers and candles at a memorial for the victims.
Meanwhile more details have emerged about why the police operation to capture the gunman took so long.
Local police said a boat they wanted to use to get to the island was too small and leaky to carry personnel and equipment, and they decided to wait for a special unit from Oslo.
And asked why a helicopter was not used, police chief Sveinung Sponheim said this would have taken longer as the nearest police helicopter was at a base in the south.
On Sunday, police briefly detained and later released several people without charge in a raid in Oslo.
Mr Sponheim told reporters the suspect had property in the area of the raid and police were looking for traces of explosives, though nothing of value was found.
In an earlier news conference, he said Mr Breivik "admitted to the facts of both the bombing and the shooting, although he's not admitting criminal guilt".
"He says that he was alone but the police must verify everything that he said. Some of the witness statements from the island have made us unsure of whether there was one or more shooters."
Mr Sponheim said police were not looking for anyone else at the moment - though they had not ruled out that the suspect might have had help.
He said Mr Breivik, who has been charged over both attacks and is due to appear in court on Monday, had co-operated during his interrogation.
Mr Sponheim confirmed that the maximum time Mr Breivik could face in prison under Norwegian law is 21 years.
At least seven people were killed in the bomb attack on the government quarter in Oslo. Soon afterwards, 85 people were shot dead as a gunman, dressed as a policeman, ran amok on the nearby island of Utoeya. An 86th person died in hospital on Sunday.
The gunman was arrested when police arrived an estimated 90 minutes after the massacre began. Mr Breivik's lawyer said his client surrendered after running out of ammunition, but police later said he still had a lot with him.
At least four people from the island camp shooting are yet to be found; it is thought some may have drowned after swimming out into the lake to escape the hail of bullets.
The BBC's Richard Galpin, near Utoeya which remains cordoned off by police, says that in the midst of Norway's worst peacetime tragedy it is a particularly harrowing time for relatives of the missing.
Some families are still waiting by the lake, he says, but others have gone home.
In Oslo, police said the death toll could rise further as bodies or body parts were in buildings damaged by the bomb but still too unstable to search.
Years of planning
Mr Breivik's lawyer Geir Lippestad told Norwegian media: "He thought it was gruesome having to commit these acts, but in his head they were necessary.
"He wished to attack society and the structure of society," Mr Lippestad said.
He added that the actions had been planned for some time.
The suspect is reported to have had links with right-wing extremists.
Still pictures of him, wearing a wetsuit and carrying an automatic weapon, appeared in a 12-minute anti-Muslim video called Knights Templar 2083, which appeared briefly on YouTube.
A 1,500-page document written in English and said to be by Mr Breivik - posted under the pseudonym of Andrew Berwick - was also put online hours before the attacks, suggesting they had been years in the planning.
The document and the video repeatedly refer to multiculturalism and Muslim immigration; the author claims to be a follower of the Knights Templar - a medieval Christian organisation involved in the Crusades, and sometimes revered by white supremacists.
Police have not speculated on motives for the attack but the bomb in Oslo targeted buildings connected to Norway's governing Labour Party, and the youth camp on Utoeya island was also run by the party.
In the document posted online, references were made to targeting "cultural Marxists/ multiculturalist traitors".
Norway has had problems with neo-Nazi groups in the past but the assumption was that such groups had been largely eliminated and did not pose a significant threat, correspondents say.