During the afternoon, three police officers were injured in a riot in Skäggetorp in Linköping, where several police cars were also vandalized.
A large number of people had gathered at the site since they were reached by the news that the Danish right-wing extremist party Stram Kurs was planning to hold a demonstration there.
The party had permission to carry out a demonstration also in Norrköping during the evening, but that permission has been withdrawn, the police announce.
Throwing stones at the police
In the Navestad district in Norrköping, masked people are moving and rockets have been fired at cars.
One person has been arrested for violent rioting.
Stones must have been thrown at both the police and the rescue service.
Pictures show riot police on site in the area.
A police source tells SVT Nyheter that they are now gathering strength for the violence, which they believe may continue well into the night.
Public transport is stopped
Östgötatrafiken has temporarily been forced to close several tram stops in Norrköping and the situation is described as very uneasy in both Linköping and Norrköping.
A tram on its way to Kvarnberget has been attacked by protesters and a car was set on fire when the tram tried to pass, according to Östgötatrafiken.
- We have chosen not to use replacement buses due to the risk of stone-throwing, says Christer Ringman at Östgötatrafiken's traffic management, and flags that you may be forced to close more stops during the evening.
- We do not know how long this will last, says Christer Ringman.