Mr. Breivik’s brief appearance at an Oslo courthouse on a cold misty day came as Norwegians were still grappling with the enormity of the attacks on Friday that amounted to one of the worst mass killings in postwar Europe. By Monday evening, at least 100,000 mourners had converged on Oslo to honor the victims and repudiate the suspect’s ideology of hatred toward Muslims and advocates of multiculturalism, who he said were ruining Norway and threatening Western European civilization.

The judge ordered Mr. Breivik held in jail for eight weeks, half of it in isolation, with no access to the outside except through his lawyer. The judge refused to open the hearing to the public, arguing that evidence could be ruined. Mr. Breivik, who had asked for an open hearing to explain his actions and his views about Muslims and to wear some sort of uniform, was denied on both counts. He was photographed in a car leaving the hearing wearing a red sweater embossed with a Lacoste alligator emblem.

Judge Heger said Mr. Breivik had been charged with “acts of terrorism,” including an attempt to “disturb or destroy the functions of society, such as the government” and to spread “serious fear” among the population. At the televised news conference, the judge said Mr. Breivik had acknowledged carrying out the attacks but had pleaded not guilty, because he “believes that he needed to carry out these acts to save Norway” and Western Europe from “cultural Marxism and Muslim domination.”

The police also revised the death toll downward to 76 from 93, saying that eight people were now known to have died in the bomb blast in central Oslo, one more than before, and 68 on the island of Utoya, instead of 86. The police said they had been too occupied with searching for the dead and missing to confirm their counts, and to prevent further confusion, they said, they declined to provide any figure for those still missing.