Norwegian police late on Tuesday said they had found and detonated a cache of explosives at a farm rented by the gunman who claimed responsibility for killing 76 people in twin attacks last week.
They refused however to disclose the quantity or nature of the explosives.
"Explosives were found on the farm," outside Olso rented by Anders Behring Breivik, police spokeswoman Trine Dyngeland told the media.
"We thought it better not to move them and they were destroyed on the spot in a controlled explosion," she said.
Behring Breivik, who said he had planned Friday's attacks for a long time, had rented the farm north of Oslo ostensibly to grow vegetables.
Norwegian media said it was a cover for him to buy large quantities of chemical fertilisers to make a bomb without attracting suspicion. He had bought six tonnes of fertiliser since the start of May, according to the fertiliser group purchasing organisation.
Behring Breivik admitted carrying out the bomb attack at the government centre in downtown Oslo and a shooting spree at a nearby island at his first court appearance on Monday when he was remanded in custody for eight weeks.
He says he was on a crusade to save Norway and Western Europe from a Muslim invasion and that the attack on the Labour Party-led government and its youth wing were ‘cruel’ but ‘necessary’.