"The investigators are looking into various online communities which might have egged on the suspect to carry out the attack," said a police source.

A 17-year-old girl was killed and three other children were injured in a sword attack at Brinell School in Fagersta. As police probe the motive and wider circumstances, the town has gathered to mourn another episode of school violence in Sweden.

Police in Sweden say the victim of a deadly sword attack at a school was a 17-year-old girl.

Police have said they have arrested an individual who stabbed several people, killing one person, with a sword at a high school in central Sweden.