Police say the shooting spree on the island of Utoya killed at least 84 people while a bomb blast outside the prime minister’s office in Oslo killed at least seven people.
Police in the Norwegian capital maintained a tight cordon around the scene of the bomb blast in the city centre.
Police have a suspect in custody and have said he has posted right-wing statements on the Internet, but Prime Minister Jens Stoltenberg cautioned that it was too soon to know the motive for the attacks.
“We will will not speculate, we will await the investigation from the police before we say anything about this particular case,” Stoltenberg told reporters at a joint news conference with Justice Minister Knut Storberget on Saturday morning.
Asked about the extent of right-wing extremism in Norway, Stoltenberg said it was not a big problem “compared to other countries”, but he acknowledged that police had been monitoring extremist groups.
Stoltenberg added that the government would convene on Saturday to discuss ways to assist those who have lost loved ones in the attacks, and to “address the question of the threat level.”
Police said a Norwegian dressed as a police officer gunned down at least 84 people at an island retreat before being arrested.
Investigators are still searching the surrounding waters, where people fled the attack, which followed an explosion in nearby Oslo that killed seven.
The mass shootings are among the worst in history. With the blast outside the prime minister’s office, they formed the deadliest day of terror in Western Europe since the 2004 Madrid train bombings killed 191.
Police told reporters that a suspect was in custody being questioned for both assaults and is cooperating with the investigators.
Though police did not release his name, Norwegian national broadcaster NRK identified him as 32-year-old Anders Behring Breivik and said police searched his Oslo apartment overnight.
A police official said the suspect appears to have acted alone in both attacks, and that “it seems like this is not linked to any international terrorist organisations at all.” The official spoke on condition of anonymity because that information had not been officially released by Norway’s police.
Norway has not changed its threat level after twin attacks on the capital and a nearby island retreat, the justice minister said.
Police said it was about 30 minutes before a SWAT team arrived on the island after the shooting began.
Police initially said about 10 were killed at the forested camp on the island, but some survivors said they thought the toll was much higher. Reporters were told early Saturday that police had discovered many more victims.
The death toll could rise even further as others were severely wounded, but police didn’t know how many were hurt.