Norwegian police have apologised for delays in their response to the massacre of 69 young people by right-wing extremist Anders Behring Breivik last July, admitting that lives could have been saved if they had intervened more quickly, The Sydney Morning Herald reported.

"On behalf of the Norwegian police I want to apologise that we did not arrest [him] sooner," the national Police Commissioner, Oeystein Maeland, said in a statement released with a report that evaluated the incident.

"Every minute was a minute too long … It is hard, knowing that so many lives could have been spared if the perpetrator had been arrested sooner."

The chief of the police district where the massacre occurred, Sissel Hammer, said police "theoretically" could have shortened Breivik's attack by 16 minutes if the response had been perfect.

Breivik set off a 950 kilogram bomb outside government buildings in central Oslo, killing eight people, before he went to the island of Utoya where he killed another 69, most of them teenagers at a summer camp.

Breivik, who has since been given a hotly challenged diagnosis of paranoid schizophrenia, claimed to be on a crusade against the "Islamisation" of Europe. His mental state is being re-evaluated and his trial is due to start on April 16.