Norwegians are paying tribute to 77 people killed in last month's bombing and shooting massacre by a right-wing extremist.

A memorial service, to be broadcast live on national television, will be attended by the families of victims and survivors of the July 22 car bombing and shooting spree.

Norway's King Harald and Prime Minister Jens Stoltenberg will also address the service that will include performances by Norwegian singers and musicians. The Norwegian government and leading politicians from neighbouring Nordic countries are also set to attend.

Today's service marks an end to a month of mourning in the Scandinavian country that was shocked by the attacks.

Nearly 1,000 survivors of the massacre on Utoya island yesterday carried flowers to the site of the killings as they remembered the joys of an island youth camp that turned into a scene of horror.

Many lit candles and laid hand-written notes in memory of their friends at the sites where they were shot during the summer camp organised by the youth wing of Norway's Labour Party.

Anders Behring Breivik has admitted killing 77 people on July 22 when he first detonated a truck bomb outside government offices in the capital, Oslo, and then went on a meticulously planned shooting spree on the island, some 25 miles away.

Breivik denies criminal guilt because he believes the massacre was necessary to save Norway and Europe.

He said the attacks were an attempt at cultural revolution, aimed at purging Europe of Muslims and punishing politicians that have embraced multiculturalism.