A Norwegian court found Anders Behring Breivik sane on Friday in the murder of 77 people in a gun and bomb massacre last year, sending him to jail for at least 21 years and dismissing the prosecution's request for an insane verdict.

Breivik, who has admitted detonating a fertilizer bomb outside government headquarters, killing eight, before gunning down 69 at the ruling party's summer youth camp, faces the possibility of indefinite extensions to his sentence.

Many survivors and victims' families wanted a sane verdict, saying the opposite would diminish his responsibility for the attacks.

Breivik said he targeted the ruling centre-left Labour Party for its support of Muslim immigration. He dismissed being called a child murderer, arguing that his victims, some as young as 14, were brainwashed activists whose support for multiculturalism threatened to adulterate pure Norwegian blood.

Breivik himself had argued for the sane verdict as he wanted the attack to be seen as a political statement.