Norwegian authorities could have prevented or interrupted the bomb and gun attacks by a far-right fanatic that killed 77 people last year, a government appointed commission said Monday.
The long-awaited report into the July 22 attacks also said the domestic intelligence service could have done more to track down the gunman, but stopped short of saying it could have stopped him.
Anders Behring Breivik, 33, has admitted to the bombing of the government's headquarters in Oslo, which killed eight people, and the subsequent shooting spree at a youth camp that left 69 dead, more than half them teenagers.
He is currently awaiting sentencing.
While noting that the attacks ''may be the most shocking and incomprehensible acts ever experienced in Norway,'' the 500-page report said the bombing ''could have been prevented'' if already adopted security measures had been implemented more effectively.
Breivik was able to park a van with a fertilizer bomb just outside the high-rise before he drove another car to the Labor Party's youth camp on Utoya, unhindered.
The report said that a car bomb scenario ''at the government complex and several coordinated attacks have been recurring scenarios in threat assessments as well as for safety analyses and exercise scenarios for many years.''
The police response was also slowed down by a series of blunders, including flaws in communication systems and the breakdown of an overloaded boat carrying a police anti-terror unit.
Meanwhile, Norway's only police helicopter was left unused, its crew on vacation.
Breivik's shooting spree lasted for more than one hour before he surrendered to police.
The report said a faster police response could have stopped Breivik's shooting spree earlier, but recognized that ''hardly anyone could have imagined'' the attack on Utoya.
''Sadly, however, after repeated school massacres in other countries, an armed desperado who shoots adolescents is indeed conceivable - also in Norway,'' it said.
Though Breivik has admitted the attacks, he rejected criminal guilt during his trial, saying his victims had betrayed their country by embracing a multicultural society.
Prosecutors have said there were doubts about his sanity and suggested Breivik be committed to compulsory psychiatric care instead of prison. A ruling is set for August 24.