The trial of  Norwegian mass murderer Anders Behring Breivik was interrupted briefly Friday when the brother one of his 77 victims hurled a shoe at him.

It was the first such outburst from the gallery in Oslo’s district court, where courtroom observers have been unusually subdued despite Breivik's own chillingly and implacably delievered account of his crimes.

However, he pleaded not guilty saying his actions were "cruel, but necessary" because his victims were traitors to Norway because they embraced multiculturalism.

Police didn’t identify the shoe-thrower in Oslo but said he was the brother of one of the victims.

Swedish journalist Mikaela Akerman told the Associated Press that forensic experts were testifying when a man in the second row suddenly stood up. 

She said Breivik remained calm and “smiled a little” as he watched security guards seize the man and lead him out of the court room.

Breivik reportedly addressed the court as proceedings resumed after a 10-minute recess. 

Ironically - while throwing shoes has long been a form of protest in many countries - it is most deeply associated in Western culture with the Breivik's hated Islam.