Anders Behring Breivik said "mission accomplished" during a call to police after he massacred 69 people on Utoya island, it has been reported.
According to the Verdens Gang (VG) daily, the 32-year-old right-wing extremist said: "Breivik. Commander. Involved in the anti-communist resistance against Islamisation.
"Mission accomplished and I will surrender to the Delta force."
The call lasted only three seconds, according to VG, which added that police attempts to get the killer back on the line had failed.
Breivik had just gone on a nearly 80-minute shooting rampage on Utoya, where the ruling Labour Party's youth movement was hosting a summer camp.
He killed 69 people and injured dozens of others, many of them teenagers, two hours after a bomb attack in nearby Oslo that left eight dead, and which he is accused of being behind.
Prosecution and defence lawyers have refused to confirm the message and it is reported the mobile phone Breivik used to make the call has not been recovered on Utoya.
Police attorney Paal-Fredrik Hjort Kraby told VG : "[Breivik's alleged call] has been one of the themes in the interviews, but I will not comment on anything beyond that."
The suggestion Breivik called police and gave notice that he would surrender will prompt speculation he intended to be taken alive.
Defence lawyer Geir Lippe City said: "I do not know what might have been his plan. He has even said that he thought the chances were small that he would come from the action alive."
Asked if Breivik was pleased with the outcome of the attacks, Mr Lippe City said: "I will not use such an expression.
"He has said that there was a plan A and a plan B. This was plan B, and he has not stated whether he was satisfied with the results or not."
The killer has described the July 22 attacks - the worst on Norwegian soil since the Second World War - as part of a "crusade" against multiculturalism and the "Muslim invasion" of Europe.