Police investigating Norway's bomb attack and mass shooting are thought to be probing the suspect's possible links to the British far right.
Detectives have been examining the background of Anders Breivik, who reportedly claimed he was recruited by two English right-wing extremists at a meeting in the UK in 2002 attended by seven other people.
The 32-year-old is due to appear in court charged with terrorism following the blast in central Oslo and gun attack at a youth camp on the island of Utoya on Friday that claimed at least 93 lives.
Breivik's lawyer said his client had wanted to revolutionise Norway's society and had "confessed to the factual circumstances" of the atrocities but denied criminal responsibility.
Meanwhile David Cameron and the Government's top security advisers will discuss Britain's vulnerability to a Norway-style terrorist attack when the Prime Minister chairs a meeting of the National Security Council on Monday morning. Scotland Yard said it was liaising with the Norwegian authorities and an officer had gone to the country to help with the inquiry.
As Breivik's possible ties with British extremists were explored, it emerged he had published a manifesto online on Friday railing against Muslim immigration to Europe and vowing revenge on "indigenous Europeans" whom he accused of betraying their heritage. He added that they would be punished for their "treasonous acts". He identified a British mentor called Richard in the 1,500-page polemic.
Asked if the Norwegian police were considering possible links to British far-right groups, a police spokesman said: "I'm sure they will do. They are following every lead and they're checking out everything he might have been associated with."
It was too early to say which groups this might include, he added. Reports suggested Breivik had connections and sympathies with the right-wing English Defence League (EDL).
But the EDL denied that the suspect had any links with it and said it "vehemently" opposed his actions. In a statement on its website the group wrote: "Terrorism and extremism of any kind is never acceptable and we pride ourselves on opposing these...
"We strongly oppose extremism and always reject any suggestion of us being either extremists or far-right, due to our great past record of dealing with anyone who holds such extremist views."