SUNDVOLLEN, Norway  - A suspected right-wing fanatic accused of killing at least 98 people deemed his acts "atrocious" yet "necessary" as Norway mourned victims of the nation's worst attacks since World War Two.

A young man is comforted as he mourns for the victims of the massacre on an island in the countryside and the bomb blast in the capital Oslo July 23, 2011. [Photo/Agencies]

Police were hunting on Sunday to see if a possible second gunman took part in the shooting massacre and bomb attack on Friday that traumatized a normally peaceful Nordic country.

In his first comment via a lawyer since he was arrested, 32-year-old Norwegian Anders Behring Breivik expressed willingness to explain himself in court at a hearing likely to be held on Monday about extending protective custody.

"He has said that he believed the actions were atrocious, but that in his head they were necessary," lawyer Geir Lippestad told independent TV2 news.

Police said Breivik gave himself up after admitting to a massacre in which at least 85 people died, mostly young people attending a summer camp of the youth wing of Norway's ruling Labour Party on an idyllic island.

Related readings: Peace in Norway shattered  Comments from leaders on Norway attacks  Norway's PM comforts attack survivors   Norway attacks shock, disgust Europe

Breivik was also arrested for the bombing of Oslo's government district. Norway's toughest sentence is 21 years in jail.

Survivors, relatives of those killed and supporters planned a procession to mourn the dead at Sundvollen on Sunday, near the island where the massacre took place.

King Harald would attend a service in Oslo cathedral, a few hundred meters (yards) from where a bomb devastated government buildings including the offices of Labour Prime Minister Jens Stoltenberg.

Lippestad, speaking late on Saturday, did not give more details of possible motives by Breivik.

About 100 people stood solemnly early on Sunday at a makeshift vigil near Oslo's main church, laying flowers and lighting candles. Soldiers with guns and wearing bullet-proof vests blocked streets leading to the government district.

"We are all in sorrow, everybody is scared," said Imran Shah, a Norwegian taxi driver of Pakistani heritage, as a light summer drizzle fell on unusually empty Oslo streets.

"At first, people thought Muslims were behind this," he said of some initial suspicions that the attacks might have been by Al Qaeda perhaps in protest at NATO-member Norway's role in Afghanistan or Iraq.

Some terrified survivors of the shooting rampage said bullets came from at least two sides.

"We are not at all certain" about whether he acted alone, police chief Sveinung Sponheim said. "That is one of the things that the investigation will concentrate on."

Police took almost 1.5 hours to stop the massacre, the worst by a single gunman in modern times. "The response time from when we got the message was quick. There were problems with transport out to the island," he said, defending the delay.

Witnesses said the gunman, wearing a police uniform, was able to shoot unchallenged for a prolonged period. He picked off his victims on Utoeya island northwest of Oslo forcing youngsters to scatter in panic or to jump into the lake to swim for the mainland.

"I heard screams. I heard people begging for their lives and I heard shots. He just blew them away," Labour Party youth member Erik Kursetgjerde, 18, said.

"I was certain I was going to die," he said. "People ran everywhere. They panicked and climbed into trees. People got trampled."

The suspect, tall and blond, owned an organic farming company called Breivik Geofarm, which a supply firm said he had used to buy fertilizer -- possibly to make the Oslo bomb.