Kenny Olsson, 27, fell off his bike in a match between his team, Vargarna, and opponents Valsarna. Olsson was leading in the eighth heat, when he was rammed up against the fence by a rider from Valsarna.
Eyewitnesses say Olsson fell off his bike and repeatedly hit his head on the fence. The heat was immediately called off and medical staff came to the scene. Olsson was given CPR before being taken in an ambulance to Vrinnevi hospital in Norrköping.
At around 10pm it was confirmed by Östergötland County Council, which runs the hospital, that Olsson had sustained serious head injuries and was critically ill.
Vargarna drivers and support staff had a crisis meeting following the accident. Torsten Sahlin, deputy chairman of the team, was asked whether all the blame should go to the rider from Valsarna:
"Yes," he replied.
"You can see quite clearly on the video that he caused him to crash into the fence."
The crash follows another serious speedway accident last month, in which 17-year-old Robin Johansson was paralyzed from the chest down.
Speedway in Sweden refers to a sport involving motorbikes in which two teams race on an unmetalled track.