Norwegian gunman Anders Behring Breivik has been taken back to the island of Utoya to stage a reconstruction of the massacre which left 69 people dead there three weeks ago and showed "no remorse".

The 32-year-old confessed killer was shackled and on a leash as he toured the site of the mass slaughter on Saturday detailing his actions to police.

"He was not unaffected by being back at the scene," reported the police prosecutor in charge of the case. "But he didn't show any remorse."

Police said the killer retraced his steps during an eight-hour visit to Utoya, providing insight into the shooting spree that would be used as evidence in the case against him as well as showing survivors and relatives exactly what happened.

"He provided us with a lot of new information which we didn't have before, despite 50 hours of (previous) interrogation," said Paal-Fredrik Hjort Kraby, prosecutor.

"We feel we now have a fairly good overview of how everyone died or was shot, even though there are still details to fill in," he said.

Under close watch by a dozen armed police, the killer retraced his steps as police helicopters circled above amid fears of an attempted revenge attack against the perpetrator of Norway's most murderous attacks since the Second World War.

Clad in a bullet proof vest over a red T-shirt, the prisoner was at times shackled with ankle cuffs and at others allowed to walk ahead tethered to a police officer by a long leash clipped to a body harness.

He was taken to the island on the same boat he used to cross the water to stage the July 22 rampage an hour after setting off a car bomb 25 miles away in downtown Oslo that killed eight people.

The prosecutor reported that Breivik's account while on the island was consistent with the interviews conducted since his arrest.

"He has been questioned for around 50 hours about this, and he has always been calm, detailed and collaborative, and that was also the case on Utoya," Mr Hjort Kraby said.

The prosecutor also confirmed Norwegian media reports that police had received several phone calls from Breivik during the hour long killing spree on the island but would not reveal details.

A report in the Norwegian daily Aftenposten, said Breivik offered to surrender several times and asked police to call him back, but they didn't.

Norwegian media also reported that Breivik may have filmed parts of the massacre himself. A video camera had been discussed during the reconstruction on Utoya, but Mr Hjort Kraby declined to elaborate.

The victims of the mass shooting had been attending an island summer camp run by the youth wing of Norway's Labour Party, which Breivik condemned in a rambling manifesto for promoting multiculturalism.

Most of the island victims were in their teens or 20s, and some were shot attempting to swim to safety, while others drowned.

Breivik's lawyer has said he has admitted to the terror attacks, but denies criminal guilt because he believes the massacre was necessary to save Norway and Europe from Muslims and punish politicians who have embraced multiculturalism.

The lawyer has said his client is "probably insane".