Police in Stockholm called in reinforcements after rioters set cars and a school ablaze in a fifth night of rioting, described as the worst in years.

About 30 cars have been torched and eight people, mostly aged in their early 20s, have been detained overnight.

Police said they needed to call in extra back-up from the cities of Malmo and Gothenburg.

The riots are mainly young people protesting over a growing divide between the rich and poor.

They claim people with immigrant backgrounds, who are poorly educated, cannot find work and feel pushed to the edge of society.

The riots started after police shot dead a 69-year-old man in the Stockholm suburb of Husby earlier this month.

Local media reported him to be a Portuguese immigrant who was suspected of wielding a large knife.

The incident prompted accusations of police brutality and violence spread to other poor neighbourhoods.

Youth unemployment is especially high in immigrant neighbourhoods like the ones where the riots have taken place.

Authorities fear violence will continue

The spree of destruction has seen masked youths vandalise schools, libraries and police stations, setting cars alight and hurling stones at police and firefighters.

Sweden's integration minister Erik Ullenhag said the priority was to return the affected neighbourhoods to normal everyday life.

"In the long run, we need to create positive spirals in these neighbourhoods," he said.

Police fear the violence will intensify over the weekend.

"We think there's going to be a lot of work and many have worked hard these last few days, so we are calling in extra police," said spokesman Anders Jonsson said.

Though far from the scale of riots in London or Paris in recent years, the violence has shocked a nation which has long taken pride in its generous social safety net.

Some seven years of centre-right rule, however, have chipped away at benefits, while some communities have struggled to cope with the wave of immigration from war-torn countries like Syria.

Locals frustrated at unrest

Students at a primary school in Kista arrived to find the inside of a small wooden classroom had been completely burnt out.

Teachers at the school said they did not know if it would be able to reopen and its 94 students will move into improvised classrooms in nearby office buildings from Monday.

"Five nights in a row - it's incomprehensible," said Faisal Lugh, whose two children attend the school.

"My children asked about the things they had there: 'How about my books? My rain jacket? My pictures? Are they all gone?'"

Many community leaders, dressed in fluorescent jackets, have taken to the streets to try to bring calm.

The brother-in-law of the man who was shot dead, Risto Kajanto, has condemned the violence.

"I want to say to all those who are burning cars that it is totally wrong to react that way," he told Swedish media.

A recent government study showed up to a third of young people aged 16 to 29 in some of the most deprived areas of Sweden's big cities neither study nor have a job.

The gap between rich and poor in Sweden is growing faster than in any other major nation, according to the Organisation for Economic Cooperation and Development, though absolute poverty remains uncommon.

Reuters