In one minute Norway came to a halt in silence tribute to mourn more than 90 victims of Friday's twin attacks in Oslo and the Utoeya island some 40 kilometers away from the capital.

From the stock market to highways and train stations, the Scandinavian nation fell in silence as it struggles to absorb the impact of its worst tragedy since the WWII.

"To remember the victims who died at the government's headquarters and on the island of Utoeya, I declare a minute of silence," Norwegian Prime Minister said before he opened a book of remembrance at a gathering at Oslo University.

The book was signed first by King Harald, Queen Sonja and Cronw Prince Haakon who were also present at the gathering with thousands of Norwegians.

Thousands more paid their respect for the deceased with flowers and candles outside the Oslo Cathedral, laying down a floral sea in the city center.

The one-minute silence was also observed in other Nordic countries on Monday.