Hundreds of youth have torched cars and attacked police in four nights of riots in suburbs of Sweden's capital, Stockholm.

Violence spread from the north to the south of the city as groups of youth pushed through Stockholm's suburbs throwing stones, breaking windows and setting cars alight.

Police in the southern city of Malmo said two cars had been set ablaze.

Local media said a police station office was set on fire in the southern Stockholm suburb of Ragsved, where several people were also detained.

No one was hurt and the fire was quickly put out.

One police officer was injured in the latest attacks and five people were arrested for attempted arson.

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.

The riots then spread from Husby to other Stockholm suburbs with high immigrant populations.

While average living standards in Sweden are still among the highest in Europe, successive governments have failed to substantially reduce long-term youth unemployment and poverty, which have affected immigrant communities worst.

Some 15% of the population are foreign-born, and unemployment among these stands at 16%, compared with 6% for native Swedes, according to OECD data.

Youth unemployment in Husby, at 6%, is twice the overall average across the capital.