Updated

Norway's domestic intelligence service had no way of uncovering the murderous plot of the "solo terrorist" behind the bomb and shooting massacre last July when 77 people were killed, officials said Friday.

The police security service, or PST, said that because Anders Behring Breivik, a previously unknown right-wing extremist, plotted the attack alone, it was virtually impossible for them to stop him.

PST was the latest Norwegian agency to evaluate its role in the country's worst peacetime massacre. The regular police force admitted for the first time Thursday that it could have stopped the killing spree faster.

Breivik has confessed to setting off a bomb that killed eight people in Oslo before massacring 69 people in a shooting rampage at a youth camp outside the capital. He denies criminal guilt, saying he's a modern-day crusader fighting a Muslim colonization of Norway.

"In our opinion Breivik is a solo terrorist, with a special view of reality and a strong will to act," PST's acting chief Roger Berg said.

PST said the only information it had about Breivik was in a December 3, 2010, email from Norway's customs agency related to an international initiative to crack down on the trade of bomb-making chemicals.

Breivik's name was on a list of 41 people who had transferred money to a Polish chemical firm, but PST said Breivik's wire payment of 121 kroner (about $20) didn't warrant further investigation.

Even if PST had made a more in-depth analysis of the list at the time, it wouldn't have found any indications that Breivik was plotting a massacre, Berg said.

Breivik will go on trial next month on terror and murder charges and is currently undergoing a psychiatric evaluation. If convicted but found insane, he would be sentenced to compulsory psychiatric care instead of prison. In either case, prosecutors say he could be locked up for the rest of his life.