STOCKHOLM, Sweden -- Riot-weary Stockholm police were reinforced on Friday with officers from other parts of Sweden as the capital prepared for more unrest after youths burned cars, schools and damaged public property in several districts of suburban Stockholm in five consecutive nights of violence.

At least 13 people, aged between 18 and 25, had been detained in connection with the disturbances which included an unsuccessful attempt to damage a police station, officers said.

"We have police officers from Goteborg and Malmo helping out now because we can't work 24/7," police spokeswoman Marie Hummer said. "We also need fresh officers as there is a busy weekend of events ahead, including a big horse race."

Officers said the violence overnight Thursday had been less intense than previous nights and that the participants seemed less aggressive.

"I've been driving around and meeting people today (Friday) and it looks calmer than before," Hummer said. "There are a lot of community people out there too and parents of youth. We have so many engaged people now, worried people."

The unrest in the Stockholm suburbs, some of which are predominantly populated by immigrants, was sparked over perceived police brutality after officers fatally shot a knife-wielding man who had locked himself in his apartment. Some residents accused police of unnecessary violence when trying to arrest him and others have said that officers, who reacted to the violence on the streets, were allegedly heard to have uttered racist slurs.

For some, the real reason for the unrest is the high unemployment and isolation of youths in the southern and western Stockholm suburbs where the violence occurred -- ones who see little future for themselves or access to Sweden's prosperity.

Despite Sweden's high living standards and its egalitarian ways, the country has seen the biggest surge in inequality of any Organization for Economic Cooperation and Development country over the past 25 years, according to a recent OECD report.

The difference is striking between native Swedes and the fast-growing immigrant population.

In Husby, the neighbourhood west of Stockholm where the violence started Sunday, around 80 per cent of the 11,000 residents are either first or second generation immigrants.