Witnesses said the man deliberately drove at speed into the crowd, and there are unconfirmed reports he then left the vehicle and attacked people with a knife. Witnesses reported he was travelling at around 60 miles per hour in a sport utility vehicle.
A man, described by regional governor Hermann Schuetzenhoefer as “deranged”, has been arrested. He is said to be a 26-year-old Austrian of Bosnian origin.
“There is no explanation, there is no excuse,” Governor Schuetzenhoefer said.
Police said initial investigation indicated the incident was not related to terrorism, adding that the man was believed to be suffering family problems.
A major emergency services operation is now underway, with local media reporting another 50 people are injured. Fourt helicopters and 60 ambulances were sent to the scene.
The square in Austria’s second biggest city was hosting an event connected to the nearby Austrian Formula One Grand Prix. Police have released no further details.