Police named the first four of 76 people killed. Although only names, ages and hometowns were listed, it will likely bring another shock to friends and acquaintances who did not already know of their deaths.
The first release of names listed three who were killed in the bomb blast in Oslo's government quarter and one killed at the island youth camp. Ages ranged from 23 to 61.
Defense counsel Geir Lippestad said his client is likely insane.
Anders Behring Breivik asked his defense counsel how many people he had killed, but Lippestad said he did not answer his question.
The death toll from the shooting spree at the island youth camp was lowered from 86 to 68, and the overall death toll stands at 76.
Two psychiatric experts will evaluate Breivik to determine whether he is mentally ill, said Lippestad, adding that it's too early to say whether that will be his defense.
"This whole case has indicated that he's insane," he told reporters.
Lippestad said Breivik believes his "operation" is going according to plan and that he views himself as a savior. Breivik views his attacks as the start of a war against Muslim domination, his lawyer said.
"He asked me if was if I was shocked and if I could explain to him what happened," Lippestad said. "He didn't know if he had succeeded with his plan."
While Breivik has confessed to last week's bombing in the capital and a shooting rampage at a Labor Party retreat, he has pleaded not guilty to the terrorism charges he faces.
Lippestad said Breivik took drugs before the attack to stay awake and alert.
About 150,000 people filled the streets of Oslo on Monday, laying roses feet deep in the street as they mourned the dead and vowed that Norway's commitment to democracy could not be shaken.
Breivik claimed he is part of an organization with several cells in Western countries, but police believe he didn't have any accomplices.
The Associated Press contributed to this story.