The Norwegian man charged with the twin attacks that claimed 92 lives said they were "dreadful, but necessary", his lawyer said Sunday, DPA reported.
The 32-year-old has been charged with the Friday shooting spree that claimed at least 85 lives, as well the bombing hours earlier in central Oslo that killed seven people.
Lawyer Geir Lippestad told reporters the suspect has "admitted the circumstances," and would offer more information on Monday at a custody hearing.
Chilling insights into the suspect's views appeared in a manifesto and video published on the internet, just prior to the deadly acts.
In the 1,500-page manuscript titled "Declaration of Independence of Europe," he outlined his views and plans in detail.
The manuscript slammed multiculturalism and stated how immigrants, especially Muslims, should be banished from Europe. It was signed with the name Andrew Berwick, likely a Anglicized version of the suspect's Norwegian name.
The suspect has not been officially identified.
In the manuscript he wrote how he experimented with homemade bombs and avoided his family and friends so that they would not detect his plans. It appeared he had started to plan his actions since 2002.
The last entry was published on Friday, a few hours before the blast in central Oslo.
Police were studying the manifesto as part of the ongoing investigation, spokesman Einar Aas told Norwegian broadcaster NRK.
The video showed the man with an automatic weapon and wearing a diving suit adorned with a badge with the inscription "Marxist hunter." The video was titled Knights Templar 2083.
The death toll could rise further as five people remained unaccounted for at the Utoya island, near Oslo, the scene of the shooting rampage where 85 people were killed. A search was ongoing in the waters off the island.
Prime Minister Jens Stoltenberg and other members of government, as well as King Harald and other members of the royal family were Sunday scheduled to attend a service at Oslo Cathedral. Flowers piled high outside the church and people also lit candles overnight.