Police in Stockholm called in reinforcements on Thursday as the Swedish capital braced for a fifth night of riots in immigrant suburbs.
The fire brigade said it was called to some 90 different blazes on Wednesday night, most of them caused by rioters.
Early on Thursday, rioters hurled rocks at a police station in the Kista district, near the suburb of Husby, where the unrest began on Sunday night.
Rocks were also thrown at two police stations south of Stockholm. A restaurant in the southern suburb of Skogaas was set on fire.
The troubles are believed to have been triggered by a fatal shooting by police of a Husby resident last week, after the man wielded a machete.
Immigrants comprise about 15% of the population of Sweden, which has a generous refugee policy. But many find jobs hard to get, despite numerous government programmes.
Prime Minister Fredrik Reinfeldt on Wednesday blamed the trouble on "hooligans" and said on Thursday they were not representative of the majority in those areas.
Integration Minister Erik Ullenhag attributed it to high unemployment and social exclusion in areas dominated by immigrants.