Police in Norway were called to what they thought was a traffic incident on Monday evening but turned out to be a bus hijacking.
They arrested a man whom witnesses said after the incident, boarded the bus wielding a knife.
Three people were found dead on the vehicle – one woman and two men.
The local chief of police Ronny Iden confirmed that three people had been killed on the bus which was travelling between Aardal and Tyin – some 220km northwest of Oslo. The man arrested was of foreign origin, but there were no further details.
The suspect was taken to the local hospital for treatment. The motive for the attack is not clear. Terrorism has been discounted, and police do not believe the victims were known to the assailant.