Swedish police say unrest erupted overnight in Goteborg, the country's second largest city, as several officers were attacked by youths hurling rocks and Molotov cocktails.
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.