A Norwegian court has found mass killer Anders Breivik not insane and has sentenced him to 21 years in prison.

The far-right extremist killed 77 people in July last year after a bomb and gun attack.

He has admitted blowing up the Oslo government headquarters with a fertiliser bomb, killing 8, before gunning down 69 at a summer youth camp of the the ruling party.

Breivik smirked as he walked into the court room in Oslo and raised his fist in salute.

The full reading of the verdict is expected to take several hours.

Breivik has also been declared sane in relation to the crime.

He will be kept in isolation inside Ila Prison on the outskirts of Oslo inside relatively spacious quarters that include a separate exercise room, a computer and a TV.

His 10-week trial focused on his sanity with prosecutors arguing he should be declared insane and held in a mental hospital and not jail.

Reading the ruling Judge Wenche Elisabeth Arntzen handed down a sentence of “preventive detention” of at least 10 years and a maximum of 21 years.

However such sentences can be extended under Norwegian law as long as an inmate is considered dangerous.

Breivik appeared to look pleased as the judge read the ruling.