Convicted Norwegian mass-killer Anders Behring Breivik has threatened to go on hunger strike unless he gets access to better video games, a sofa and a larger gym, according to the Associated Press

In a letter sent to media, Breivik wrote that the hunger strike will continue until his demands are met or he dies.

Breivik's lawyer Tord Jordet confirmed the letter was authentic and said his client is waiting for a response from prison authorities before starting the hunger strike.

Breivik is serving a 21-year prison sentence, which can be extended when it expires, for killing 77 people in bomb and gun massacres in 2011.

Among his demands, Breivik wants communication restrictions lifted and improved air conditions. He wants the available PlayStation 2 console replaced by a modern version.