The fourth day of Norway’s trial of the century begins with Anders Behring Breivik telling the court he originally planned to detonate three car bombs.

The sole car bomb Anders Breivik did set off killed eight people in Oslo. The mass killer said he decided against multiple bombs because building them was “more difficult than [he] had thought”.

Anders Breivik disputed a psychiatrist’s report describing him as insane.

Earlier, he told the court he took a year off to play World of Warcraft.

Anders Breivik described using computer games to rehearse scenarios before setting off the car bomb outside a government building in the Norwegian capital on 22 July 2011.

He said his initial targets for the three bombs were government headquarters, Labour Party offices and the royal castle, but not the royal family itself.

The fourth day of Norway’s trial of the century begins with Anders Behring Breivik telling the court he originally planned to detonate three car bombs

Anders Breivik followed his car bomb attack with a mass shooting at a Labour Party summer camp on Utoeya island, killing 69 people, many of them teenagers.

He told prosecutors he came up with idea of targeting Utoeya when it became clear that it was impossible to make more than one bomb.

Anders Breivik said he decided to choose one target for a bomb and one “based on a firing operation”.

He also considered a congress of journalists and the Labour Party summer conference.

Anders Breivik described how he joined a gun club in 2010 as part of his preparations.

He told the court he had begun planning a “suicide action” as far back as 2006.

He had expected he would have to fight his way out of the scene of the bombing and estimated his chance of survival at 5%, he said.

However, the prosecution asserted Anders Breivik began preparing his attacks no earlier than 2009.

Arriving in court, Anders Breivik made no far-right salute, unlike previous days. His lawyers had asked him not to salute.

He is behaving differently from his irritable performance on Wednesday: he is answering most of the questions put to him and seems calm.

Anders Breivik has admitted the killings but denies criminal responsibility, saying he acted to protect Norway and Europe from multiculturalism.

“Militant nationalists in Europe are divided,” Anders Breivik told the court on Thursday.

“Half of them think we should attack Muslims and minorities, the other half that we should attack elites, those responsible, and hold them accountable.”

In other points so far, Anders Breivik said:

• he was 15 when he became skeptical of Muslim immigration, and 18 or 19 when he first thought about committing violence

• he named his manifesto 2083 to represent the 400th anniversary of the Battle of Vienna, when the Ottoman Turks were defeated

• he named the guns he used in the Utoeya shootings after characters in Norse mythology

• he joined the Masons as soon as he was old enough because they were a “Christian organization that protects its members”

• he took a year’s “sabbatical” from business activities in 2006 because he was planning the “suicide action”

• he spent the year playing the online role-play game, World of Warcraft, for up to 16 hours a day

The court heard that Anders Breivik formed a company in the Bahamas that he used as a front for money-laundering. The funds were intended for nationalist activities.

The court is seeking to determine whether Anders Breivik is sane. If so, he will be jailed for at least 21 years, although that sentence can be extended by the courts.

If he is deemed insane, he will be committed to a psychiatric institution.

Survivor Bjorn Ihler, who was on Utoeya island when Anders Breivik went on his shooting spree, said it was getting “easier and easier” to see him in the dock.

“All the things he did and said disarms him in so many ways… he gets less and less dangerous in my mind,” Bjorn Ihler said.

Anders Breivik’s evidence is scheduled to last five days, concluding on Monday.