As the nation struggled to absorb the impact of its worst postwar tragedy, thousands of people bowed their heads in silence outside Oslo's main university at a ceremony led by Prime Minister Jens Stoltenberg and King Harald V.
"To remember the victims who died at the government's headquarters and on the island of Utoeya, I declare a minute of silence," said Stotenberg on the stroke of midday before he then opened a book of condolence.
The country's train stations closed and the stock market halted trading. Nordic neighbours Sweden, Finland, Denmark and Iceland also held a minute's silence and flew national flags at half-mast.
"It was an attack against the very values that our countries are built upon. It was an attack against all of us," said Danish Prime Minister Lars Loekke Rasmussen.
Anders Behring Breivik has already confessed to the killings but denied criminal responsibility, according to his lawyer.
The 32-year-old was to make his first appearance in a downtown court around 1:00 pm (1630 IST), for arraignment over Friday's car bombing and mass shooting that he said he had planned over a long time and executed single-handedly.
A court official said that the judge had ordered the hearing to take place behind closed doors, against Behring Breivik's wishes.
