Updated

Accepting a sentence that could keep him imprisoned for life, Anders Behring Breivik apologized Friday for not killing more people in a bomb and gun massacre that left 77 people dead.

Breivik's gruesome and defiant statement could mark the end of a legal process that has haunted Norway for 13 months.

Prosecutors said they had not decided whether to appeal the ruling by Oslo's district court, which declared the right-wing extremist sane enough to be held criminally responsible for attacks "unparalleled in Norwegian history."

"Since I don't recognize the authority of the court I cannot legitimize the Oslo district court by accepting the verdict," Breivik said. "At the same time I cannot appeal the verdict, because by appealing it I would legitimize the court."

Then, Breivik said he wanted to issue an apology, but it wasn't for the victims, most of the teenagers gunned down in one of the worst peacetime shooting massacres in modern history.

"I wish to apologize to all militant nationalists that I wasn't able to execute more," Breivik said.

Earlier Friday, Breivik smiled with apparent satisfaction when Judge Wenche Elisabeth Arntzen read the ruling, declaring him sane enough to be held criminally responsible and sentencing him to "preventive detention," which means it is unlikely he will ever be released.

The sentence brings a form of closure to Norway, which was shaken to its core by the attacks on July 22, 2011, because Breivik's lawyers said before the verdict that he would not appeal any ruling that did not declare him insane.

But it also means Breivik got what he wanted: a ruling that paints him as a political terrorist instead of a psychotic mass murderer. Since his arrest, Breivik has said the attacks were meant to draw attention to his extreme right-wing ideology and to inspire a multi-decade uprising by "militant nationalists" across Europe.

Prosecutors had argued Breivik was insane as he plotted his attacks to draw attention to a rambling "manifesto" that blamed Muslim immigration for the disintegration of European society.

They said Friday they needed time to review the ruling before deciding on whether to appeal.