STOCKHOLM (AP) - Groups of youths have burnt down a restaurant, torched more than 30 cars and injured three police in a fourth night of riots in suburbs of the Swedish capital that started following a fatal police shooting.

Police spokesman Kjell Lindgren says at least 30 cars were set ablaze across western and southern Stockholm early on Thursday. Firefighters said they have "never before seen so many fires raging at the same time". Fire also destroyed a restaurant in Skogas, south of Stockholm.

Spokesman Lindgren says a 16-year-old girl was briefly detained on suspicion of preparing an arson attack, but was later sent home to her parents.

The unrest began on Sunday in response to the May 13 shooting, in which police killed a 69-year-old, knife-wielding man in a northwestern suburb.