Police say no one was seriously injured in the attacks, but at least two police officers reported burned eyes after being targeted by a green laser light.
It was not immediately clear what provoked the unrest, but police say two people were arrested for vandalizing a streetcar just before midnight Tuesday and this could have sparked the melee.
Two police cars were vandalized and one other car was incinerated.
Police spokesman Lars-Gunnar Gustafsson said Wednesday that no arrests have been made.
