OSLO - Norway's Prime Minister Jens Stoltenberg said on Saturday he did not want to speculate on the motives for a bomb blast and a shooting that killed at least 91 people, mostly teenagers.

"Compared to other countries I wouldn't say we have a big problem with right-wing extremists in Norway. But we have had some groups, we have followed them before, and our police is aware that there are some right-wing groups," he told a news conference.

A gunman killed at least 84 people at a youth camp of Norway's ruling political party on Friday, hours after a bomb killed seven in the government district in the capital Oslo. Police suspect the gunman is involved also in the bomb blast.

Justice minister Knut Storberget said Norway had not raised its national threat level following the Friday attacks.