Killings were necessary, claims Norway gunman
He has, however, not pleaded guilty, authorities said Sunday.
The gunman told investigators he acted alone and that there was no accomplice, acting National Police Chief Sveinung Sponheim has said, reported CNN.
The suspect, identified as Anders Behring Breivik, a 32-year-old Norwegian, went on a killing spree Friday evening at a youth camp on Utoya Island leaving at least 85 people dead. The massacre took place shortly after a bombing in Oslo left seven people dead.
Geir Lippestad, who claimed to represent Breivik, said late Saturday that his client "is ready to explain himself" Monday at a court appearance.
"He (Breivik) thought it was gruesome having to commit these acts, but in his head they were necessary," Breivik's lawyer Geir Lippestad told the Norwegian media.
Lippestad said the attack had been planned "for some while", reported BBC.
Charged with terrorism, Breivik is due to appear in court Monday.
Memorial services were held across the country, including at the main Lutheran cathedral here.
Norway's King Harald V and his wife Queen Sonja attended the cathedral, along with Prime Minister Jens Stoltenberg, reported BBC.
The media report said that the police have not speculated on the motive. The bomb in Oslo targeted buildings connected to Norway's governing Labour Party while the youth camp on Utoeya island was also run by the party.
A 1,500-page manifesto, purportedly written by Breivik, shows his right-wing extremist views.
In it, he vows that a "European civil war" will lead to the execution of "cultural Marxists" and the banishing of Muslims, reported CNN.
The document gives details of Breivik's background and his plans to commit Friday's attacks.
"If you are concerned about the future of Western Europe you will definitely find the information both interesting and highly relevant," he wrote.
The document is titled "2083: A European Declaration of Independence". It is a date which Breivik believes that an European civil war will end with the execution of cultural Marxists and the deportation of Muslims.
This "civil war" would come in three phases, he claims.