"It was the third night of unrest, mainly in suburbs where many immigrants live.
The riots, in one of Europe's richest capitals, have shocked a country that prides itself on a reputation for social justice, and fuelled a debate about how Sweden is coping with both youth unemployment and an influx of immigrants.
"We've had around 30 cars set on fire last night, fires that we connect to youth gangs and criminals," Kjell Lindgren, spokesman for Stockholm police, said on Wednesday.
He said eight people had been arrested on Tuesday night, but there were no reports of injuries.
The riots appear to have been sparked by the police killing of a 69-year-old man wielding a machete in the suburb of Husby this month, which prompted accusations of police brutality."