Officials said rioters set cars on fire and threw stones at police officers and firefighters Tuesday, Swedish news agency Tidningarnas Telegrambyra reported Wednesday.
The rioting Tuesday spread to areas that hadn't been affected in the two previous days of unrest, Stockholm Police official Kjell Lindgren told Aftonbladet.
"It feels like people are taking the opportunity in other areas because of the attention given to Husby [a Stockholm suburb]," Lindgren said.
Rioters also damaged Jakobsberg police station and a nearby shopping center, TT reported.
An organization in Husby, where the riots began, said the troubles arose from frustration about the fatal police shooting of a 69-year-old man in Husby, a largely immigrant area, last Monday.
"You have to see what happened from a wider point of view. It's not the first time something like this has happened and it's not the last. This is the kind of reaction when there isn't equality between people, which is the case in Sweden," Rami al-Khamisi, founder of local youth organization Megafonen, told The Local.
Swedish Prime Minister Fredrik Reinfeldt, during a news conference Tuesday, warned the protesters about continued rioting.
"We have groups of young men who think that that they can and should change society with violence," Reinfeldt said. "Let's be clear: This is not OK. We cannot be ruled by violence."