Norwegian Prime Minister Jens Stoltenberg told hundreds of mourners at a memorial mass in Oslo Cathedral that the scale of the evil of the twin attacks in Norway was yet to emerge.

Mr Stoltenberg told the crowd, who included the King and Queen of Norway, that the names and photographs of those who died would soon be released and 'the scale of the evil will then emerge'.

'We are a small country but we are a proud people,' he said, adding that Norway 'will never abandon its values'.

Mr Stoltenberg addressed a memorial mass for the 93 known victims of Friday's twin bomb and gun attacks, attended by King Harald V, Queen Sonja and other leaders, saying 'each and every one of those who is gone is a tragedy'.

Hundreds of people had gathered outside the cathedral where a shrine has been set up amid a sea of flowers laid in tribute to those killed in the bombing in Oslo and a mass shooting on nearby Utoeya island.

Five people are still unaccounted for following the attacks.

Massacre

Police are hunting to see if a possible second gunman took part in the shooting and bomb attack.

In his first comment via a lawyer since he was arrested, 32-year-old Norwegian Anders Behring Breivik expressed a 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 86 people died, mostly young people attending a summer camp of the youth wing of Norway's ruling Labour Party on an idyllic island.

Breivik was also arrested for the bombing of Oslo's government district that killed seven people hours earlier. Norway's toughest sentence is 21 years in jail.

Survivors, relatives of those killed and supporters are planning a procession to mourn the dead at Sundvollen later today, near the island where the massacre took place.

Police said they were seeking several missing people and the toll could rise to 98.

Details emrging about the killer suggest Breivik hated ‘cultural marxists’, wanted a ‘crusade’ against the spread of Islam and liked guns and weightlifting, web postings, acquaintances and officials said.

A video posted to the YouTube website showed several pictures of Breivik, including one of him in a Navy Seal type scuba diving outfit pointing an automatic weapon.

‘Before we can start our crusade we must do our duty by decimating cultural marxism,’ said a caption under the video called Knights Templar 2083 on the YouTube website, which has since been taken down.

A Norwegian website provided a link to a 1,500 page electronic manifesto which says Breivik was the author. It was not possible to verify who posted the video or wrote the book.

‘Once you decide to strike, it is better to kill too many than not enough, or you risk reducing the desired ideological impact of the strike,’ the book said.

Vigil

Norway has traditionally been open to immigration, which has been criticised by the Progress Party, of which Breivik was for a short time a member. The Labour Party, whose youth camp Breivik attacked, has long been in favour of immigration.

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.

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.