Just before 11pm an explosive device was thrown into the court building through a window. Around ten windows were shattered by the blast and a stone staircase inside was damaged. Nobody was injured.
Directly after the explosion a witness saw a man hurrying away from the scene.
“He was described as being 180 to 190 centimetres tall, with a slim build and dressed in dark clothes, said detective Jeanette Lisjak at Norrmalm police.
Police urged the man, or other witnesses who may have seen something unusual on Riddarholmen last night to contact them.
The kind of explosive used in the attack has not yet been identified by police.
“There’s not much left of the device but there will be a forensic investigation,” said Lisjak.
According to Jeanette Lisjak the appeal court did not receive any form of threat before the attack and no motive has yet been suggested.
Earlier on Friday the court delivered its verdict in a high profile case concerning the death of a 29 year old man on Kungsgatan, a central Stockholm street, last May.
The court found three men guilty of manslaughter and sentenced them to four years in prison.
“We don’t know if this is linked but we’re bearing it in mind,” said Jeanette Lisjak.