Anders Behring Breivik smiles during his trial in Oslo (Reuters / NTB Scanpix)

Norwegian mass killer Anders Behring Breivik carved the names of the weapons of Norse gods into his guns before killing 77 people, a court has heard.

Witnesses described how far-right extremist Breivik imitated a police officer to gain access to Utoya island, before slaughtering 69 people.

The far-right fanatic is on trial after killing 77 people in a bomb attack in central Oslo and a lengthy gun rampage on the island, where a camp was being held for young members of the country's Labour Party.

On the 11th day of Breivik's trial, the court heard how the killer tricked ferry captain Jon Olson into taking him across to the island in the hours following his bomb blast on 22 July, 2011.

Olson told the court that nobody suspected Breivik, who boarded the ferry as emergency services scrambled to respond to the explosion outside government buildings, which killed eight people and left dozens injured.

The court heard of Olson's "angst and full panic" as he tried to contact police when he became aware of the attack taking place on the island, as Breivik methodically hunted and executed his trapped victims.

Images of the killer's weapons were shown to the court, including a pistol which had the word Mjolnir carved into the handle - the name of the hammer of Thor, the Norse god of thunder.

Breivik's gun with an engraved handle (Fwalloe)

A picture was also shown of the rifle he used, which had a bayonet affixed to the end. The word Gungnir, the name of Norse god Odin's spear, was carved into it.

Breivik's rifle with Gungnir carved into it (Fwalloe)

The court also saw the fake police outfit that Breivik wore to trick his way on to the island. During his unflinching testimony, which moved many in the court to tears, Breivik described how he used the uniform to trick his scared victims to approach him for help, before gunning them down.

Uniform Breivik wore to trick his way on to Utoya island (Fwalloe)

The level of detail involved in the court process reflects Norway's staunch promise to adhere to its liberal legal system. The country pledged to respond to Breivik's attack, which he said was based on a perceived war on multiculturalism, with even greater democracy.

Mark Lewis, a reporter in the Oslo courthouse, tweeted updates on the day's events. He said: "Prominent paper editor here tells me this is a necessary catharsis for Norway. 'We need to know we have the whole truth' he says."

A previous day of the trial was marked by more than 40,000 protesters coming out and singing songs in favour of multiculturalism close to the courthouse.

Breivik, who is charged with terrorism and premeditated murder, admits the 77 killings but denies legal culpability. A majority vote of three of the five judges will be required in the trial, which is aiming to determine Breivik's sanity and therefore his legal culpability, with a verdict expected in mid-July.

He has refused to accept the court's authority and has asked for an acquittal, as he committed the killings in a pre-emptive attempt to stop a war over multiculturalism in Norway. He branded the Norwegian maximum sentence of 21 years as pathetic and claimed he would rather be executed.

Sentences can be extended if a criminal is considered a menace to society. If declared insane by the court, he would be committed to psychiatric care. Both sides can appeal.

The trial continues.