Unrest in Stockholm’s suburbs continued for a fourth night as rioters showed their anger over a police shooting a week ago by setting fire to cars and buildings and pelting emergency workers with stones.

As many as 30 cars burned in the Swedish capital’s southern suburbs, while 11 were set alight in the Husby area, north of the city centre, where the violence broke out four days ago, police spokesman Kjell Lindgren said by phone today. Police detained one person, a 16-year-old girl suspected of preparing an act of arson. That followed eight arrests since Tuesday.

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

“We’re hoping that there will be moderation also in the southern parts but we will continue to show our presence in the suburbs with strengthened resources.”

The unrest started May 19th in Husby - an area constructed in the 1970s and dotted with high-rise apartment blocks - about a week after police killed a 69-year-old man brandishing a knife.

Sweden, where immigrants bear the brunt of Scandinavia’s highest unemployment rate, has suffered similar bouts of unrest before. In 2008, rioters in Rosengaard in the southern city of Malmoe clashed with police after setting fire to cars and bins.

Those riots also spread to Stockholm’s Tensta and Husby suburbs. Last night, firemen trying to rescue a restaurant in Skogaas were attacked by stone-throwing youths. Police officers were also attacked in Husby.

Several other suburbs also reported vandalism and fires.

Three police officers suffered minor injuries from rocks, Mr Lindgren said. None of them required hospital care, he said. In Raagsved, 11 people were also detained before being taken away in police buses.

Police are working to identify more rioters, many of whom were masked. There were similar scenes on Tuesday, when about 30 cars were set on fire in some of Sweden’s most ethnically diverse suburbs, also including Norsborg and Vaarberg.

A Husby school and a cultural centre were set alight while bins burned across other suburbs. A school was set on fire in Skaerholmen and a police station and buildings in central Jakobsberg were vandalised. The average age of people arrested on Tuesday was about 20, police said. Unemployment is higher among immigrants in Stockholm than residents born in Sweden.

Among immigrants from countries outside the European Union, the percentage of people out of work or in job programs was 16.5 per cent in 2011, compared with 5.7 per cent for ethnic Swedes, according to Statistics Sweden. Last year, 23 per cent of municipal Stockholm’s 881,235 inhabitants came from outside Sweden, the same percentage as in Gothenburg.

Bloomberg