"They have helped a lot in reducing the unrest," Stockholm police spokeswoman Karin Solberg told Swedish news agency TT.
Sweden has since the 1980s had a network of volunteers called "Nightwalkers", usually made up of parents who walk the streets of their own suburbs in groups on weekend nights, talking to youngsters and simply making their presence known.
With their distinctive neon yellow windbreakers, their presence is aimed at deterring neighbourhood kids from getting into trouble.
They have no special authority to intervene if trouble arises, are armed only with flashlights and wear no uniform other than their colourful jackets.
In the six nights of riots that have left cars and buildings torched in Stockholm's immigrant-dominated suburbs, the volunteers' mission has been to protect schools, libraries and youth centres.
"We have changed our strategy. In the beginning, we would walk around in the neighbourhood. Now we stay put," explained Aleks Sakala, a 44-year-old IT consultant from Kista who was on Nightwalker duty on Friday night.
Kista is a mixed suburb, known as Stockholm's Silicon Valley for its high-tech industry, where telecoms giant Ericsson has its headquarters. But it is also home to a large low-income immigrant population.
It also borders Husby, where the riots broke out on May 19, triggered by the fatal police shooting of a 69-year-old resident after the man wielded a machete in public.
Local activists said the shooting sparked anger among youths who claim to have suffered from police brutality and racism.
Sakala spent the night between Friday and Saturday outdoors in the courtyard of a Kista nursery school, keeping an eye out for troublemakers under the moonlight.
The nursery school is "an ideal target", he said.
About 100 Nightwalkers were out in Kista, easily visible in the dark with their neon jackets.
Meanwhile no police officers were to be seen, despite an announcement of police reinforcements brought in from other parts of the country. Police have from the beginning tried to avoid confrontation and clashes with the rioters.
Shortly after midnight, a police patrol car pulled into the Kista nursery school parking lot, leaving again shortly afterwards.
David, a 46-year-old Nightwalker, said residents needed to take responsibility for their neighbourhoods.
"Police are not here to guard buildings. They don't have the means, and it's not their role," he said.
"I'd rather live in a society where citizens protect themselves, rather than in a society that needs police for everything. That is democracy and freedom," added Sakala.
The Nightwalkers are not always successful. On Thursday night, rioters torched a nursery school in Kista where Sakala's son is enrolled. The damage was extensive.
A group of four young women patrolling Kista on Friday night told Sakala that "everything's calm." He reminded them that "just before the nursery fire everything was perfectly calm too."
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