FIFTH UPDATE: A powerful explosion outside Norwegian government headquarters and a mass shooting at a political Party youth camp have left the residents of Oslo in shock.
Several people have been found dead inside government headquarter buildings following today's terror bomb attack at 15:26, adding to the two killed and 15 injured (video shot in the aftermath below). A number of youths were also shot dead by a man posing as a policeman at Labour's (Ap) annual summer camp on Utøya oustide the capital. 10 people are confirmed dead, according to NRK.
"A man in police uniform lured youths towards him, saying "come here", and routinely executed them afterwards," witnesses tell NRK's reporter at the scene.
The individual has now been arrested, and police say this evening they believe the two attacks are linked. However, investigators have no motive or theories as to who is responsible for the bomb. Officers at today's preliminary press conference from Grønland police station said they received no warnings in advance of the explosion. The terror threat level has now been increased.
"We recommend members of the public leave the centre of Oslo and avoid gathering in large groups. People should travel calmly home or back to their hotel, and stay there until we have cleared the matter up." Limited mobile use has also been advised.
Whilst the situation remains unclear, technicians, bomb experts and the fire department are now combing the scene for any possible clues, as well as to see if there are other explosive devices.
"All possible personnel are now on duty, and several others have been recalled from their holiday," police say.
The bomb, believed to have been contained in a delivery van parked nearby, was the first major attack on Norwegian soil since WWII. Ullevål University Hospital is on full alert.
It is thought the action was directed against the Ministry of Petroleum and Energy in Einar Gerhardsens plass, though this has not yet been confirmed.
Prime Minister Stoltenberg, who was unharmed by the attack, tells NRK by phone, "this is a very serious situation. All available emergency personnel are at the scene and my thoughts go to those who have been hit by it [the attack]."
The government's crisis advice committee is assembled to decide the next course of action, together with Minister of Justice, Knut Storberget, Health Minister Anne-Grete Strøm-Erichsen, and Jonas Gahr Støre. PM Stoltenberg says he is in continuous contact with Minister of Defence Grete Faremo. Preparedness at Oslo Gardermoen Airport has been increased.
Meanwhile, police ask members of the public with any information about the bomb to contact them on 22 66 99 66. Concerned relatives and friends can call 815 02 800.
Further updates to follow.