In this May 21, 2013 file photo, firemen extinguish a burning car in the Stockholm suburb of Kista after youths rioted in several different suburbs around Stockholm for a third executive night. (Fredrik Sandberg/AP)

Rioters outside Stockholm burned cars and trash cans, attacked schools and pelted emergency workers with rocks in a fourth night of violence sparked by a police shooting in one of Sweden’s most ethnically diverse suburbs.

As many as 30 cars were on fire in the Swedish capital’s southern suburbs, while 11 were ablaze in the Husby area, north of the city center, where the unrest broke out Sunday, police spokesman Kjell Lindgren said by phone Thursday. Police detained a 16-year-old girl suspected of planning arson. That followed eight arrests since Tuesday.

Violence erupted about a week after police shot a 69-year-old man brandishing a knife in Husby, an area dotted with high-rises built in the 1970s. The suburb is home to about 12,000 people, 60 percent of whom were born outside Sweden.

Sweden, where immigrant unemployment is about twice the national average, has suffered similar unrest before. In 2008, rioters clashed with police outside the southern Swedish city of Malmoe and in Stockholm’s Tensta and Husby suburbs.

“While the situation has become better in Husby, where a lot of local people have become engaged to calm things down,” Lindgren said, it “has intensified on the southern side of the city.”

On Wednesday night, firefighters trying to save a restaurant in Skogaas, south of Stockholm, were attacked by stone-throwing youths. Police officers were also attacked in Husby, and several other suburbs reported vandalism and fires.

“I don’t know the reasons behind what’s happened, but perhaps these people didn’t go to school, didn’t apply for jobs and just haven’t tried,” Adam Khoder, a member of Prime Minister Fredrik Reinfeldt’s Moderate Party for the local Rinkeby-Kista council, said in an interview. But he added, “This is about a few criminal youths, not entire neighborhoods.”

The family of the man who was killed by police has urged rioters to stop.

It’s “the wrong way to react,” said Risto Kajanto, the dead man’s brother-in-law, according to Swedish tabloid Aftonbladet. “Violence only feeds more violence.”

Police must admit their mistakes in the shooting, Kajanto said. The deceased man, who emigrated from Portugal in the 1970s and his wife, who came from Finland, had been out eating in a restaurant on the day he was killed, according to Aftonbladet. On the way home, they were threatened by a group of youths, prompting the man to get a knife. He was later shot by police in his apartment, according to the newspaper.

— Bloomberg News