The suspected hijacker, a 31-year-old man, was disarmed without a fight once the authorities arrived. He has been flown by helicopter to hospital in Bergen, where he is being treated for knife injuries.
The emergency services first received reports of a traffic accident involving a bus at 5.30pm. Once the fire services arrived, however, they realized that the situation was more serious.
"The bus was on the side of the road, so we stopped our car and ran over," one of those on the scene told the Norwegian broadcaster TV2. "It was impossible to open the doors."
"Then we saw a dark-skinned person inside the bus. At first, we thought he was trying to get out but then saw he was moving around with a knife, and we realized that the situation was quite different."
According to police, the man surrendered to the firemen without a struggle and was held by them until 6.45pm when the first police arrived, one hour and 15 minutes after they were first notified.
"The person came out voluntarily from the bus and was arrested by the firefighters. He had already thrown down the knife," Magne Knutsen of the Årdal police told the VG daily.
The bus, the Valdres Express, plies the four-hour journey from the mountainous region of Valdres to Oslo and was hijacked between the towns of Årdal and Tyin in Sogn og Fjordane county.
The victims included the driver, a Norwegian man in his 50s, a Swedish man in his 50s and a 19-year-old Norwegian girl. Police believe that they were the only passengers.
The attack marks the second time the Valdres Express has been hijacked. In 2003, it was hijacked by a mentally disturbed 26-year-old man who stabbed the driver to death.