Mass murderer Anders Behring Breivik now renounces violence, his lawyer said, the same day Norway commemorated the third anniversary of the massacre in which he killed 77 people.

Breivik "has now become very clear that he doesn't support violence and that he doesn't encourage others to carry out violent acts," his lawyer Tor Jordet told local media.

Breivik, 35, committed the bloodiest massacre in Norway since the end of World War II on 22 July 2011.

He killed eight people with a bomb near a building housing the left-wing government in Oslo, and then opened fire on a Labour Youth camp on the island of Utoeya, killing 69 people, most of them teenagers.

At the time, he said his actions were "cruel but necessary" to save Europe from Islam and multiculturalism.

The right-wing extremist is serving 21 years in prison, the maximum sentence in Norway, which could be extended indefinitely as long as he is still considered a threat to society.

When questioned, Mr Jordet declined to elaborate, and said the anniversary should be centred on the survivors and the victims' families.

"We have looked long and hard at what happened on 22 July and the malfunctions [of the police], but we haven't managed to discuss the thoughts of the perpetrator," Labour Youth president Eskil Pedersen said.

"Three years after the attacks, racism is back in public discussion forums and extreme-right parties win elections in countries around us."

There's a growing debate in Norway on the need to discuss the ideology behind the massacre.

"We cannot protect ourselves from all dangers with security measures," Prime Minister Erna Solberg said.

"The most important thing we can do is to confront radicalism and violent extremism by promoting the best qualities of our society."

In the presence of former Labour prime minister Jens Stoltenberg, who led the country at the time of the attacks, Ms Solberg laid a spray of flowers and led a minute's silence outside the building where the first attacked occurred.

The government decided in May to restore the still derelict building rather than demolish it, which could have been seen as a victory for Breivik.

The island of Utoeya was open today for the gathering of survivors of the shooting and relatives of the victims.

Three young survivors of the Utoeya massacre were elected to parliament last year.