Conditions were chaotic when police got their first report of the incident around 4:15pm.
Witnesses said a man suddenly went amok and attacked around six persons on the tram as it travelled near the old Bislett Swimming Pool building. It lies next to the stadium of the same name that recently was torn down for redevelopment.
The man then was said to have jumped off the tram and forced a passing car to stop. He then stabbed the driver of the car before stealing it and driving off.
"A man armed with a large knife threatened the owner of the car and stabbed him, before stealing the car," operations leader Vidar Hjulstad of the Oslo Police District told news bureau NTB. The car was found a short time later, abandoned near Hartvig Nissens School in the fashionable Frogner district.
The assailant was described as a thin man with African features, wearing a striped sweater. He's believed to be in his 40s.
Police launched a massive search for him using both dogs and a helicopter.
Survivors of the stabbing spree were rushed to both Aker and Ullevål university hospitals for treatment.
