OSLO (AFP) - A man set himself on fire on Tuesday outside the Oslo courthouse where Anders Behring Breivik is on trial for killing 77 people in twin attacks last July, police said.

The man, whose identity was not revealed, suffered serious injuries, Norwegian police said.

"The man crossed the street and set himself on fire," Kjell Jan Kvarme, head of police security operations outside the courthouse, told AFP.

"Police officers pulled off his clothes and put out the fire."

Commercial broadcaster TV2 quoted a witness as saying the man had shouted in Swedish: "Shoot me! Shoot me!"

The incident took place at 1:42 pm (1142 GMT) and the man was taken to Ullevaal Hospital, police said.

Kvarme said the man was seriously injured, adding that his motive was not known and that there was no evidence so far to say it was linked to the Breivik trial.

Inside the courthouse, on the 19th day of Breivik's trial, young people wounded in his massacre were testifying about the shooting spree on the island of Utoeya on July 22.

Breivik has been charged with committing terrorist acts when he bombed a government building in Oslo, killing eight people, before shooting dead another 69 in his rampage on Utoeya.

The victims were there for a summer camp of the ruling Labour Party's youth wing, and the youngest had just celebrated her 14th birthday.

Breivik has confessed to the killings but has refused to plead guilty, insisting the shootings were "cruel but necessary" to stop the Labour Party's "multicultural experiment" and the "Muslim invasion" of Norway and Europe.