Norway has been shocked after twin terror attacks killed at least 17 people on Friday.
Police said late on Friday that at least nine or ten victims died in a shooting at a youth camp for the ruling Labour Party on Utoeya Island, just outside Oslo.
Prime Minister Jens Stoltenberg had been set to visit the camp on Saturday.
The gunman has been arrested and is being questioned by police. He is Norwegian and was wearing a blue sweater with a police badge sewn on when he opened fire. Officials say the suspect is not a former officer.
Earlier on Friday, a bomb tore through the Norwegian capital, causing huge damage to government buildings. At least seven people died in the blast and several dozen were injured. Medics have appealed for blood donations.
Detectives believe the two attacks are linked. No group has claimed responsibility for the killings.