Prime Minister Jens Stoltenberg of Norway has praised the rule of law in the trial and sentencing of Anders Behring Breivik.
Mr Stoltenberg said it's been difficult for many to hear the details, but it is necessary in a society governed by law.
Breivik admitted killing 77 people and wounding more than 240 others in central Oslo and then at an island youth camp last year. Eight died in Oslo and 69 on the island of Utoeya.
He insisted he was sane and refused to plead guilty. The trial began in March and lasted for 10 weeks.
A court in Oslo on Friday sentenced him to 21 years in prison.
Breivik, 33, carried out the meticulously planned attack on 22 July 2011, wearing a fake police uniform, and methodically hunted his victims.
The five judges were unanimous in ruling that Breivik was sane. He was convicted of terrorism and premeditated murder, and given the maximum sentence of 21 years.
The BBC reports Breivik says he will not appeal against the verdict and sentence.
He will serve the sentence at Ila Prison near Oslo, where he has been held in isolation for most of the time since his arrest.
His actions ignited a debate about the nature of tolerance and democracy in Norway.