On Monday night, ten vehicles in the capital were targeted by a group calling itself The Indians of the Concrete Jungle.
As has become customary in recent months, the activists made their point by letting the air out of the tyres of Sports Utility Vehicles. According to police, the tyres are sometimes slashed before the environmentalists move on to their next target.
Since the summer, the group has claimed responsibility for hundreds of attacks on SUVs in an attempt to tackle what its members describe as "one of the most provocative and insane sources of unnecessary carbon emissions".
"If selective SUV-disarmament is done repeatedly and on a massive scale, it will develop from a slight annoyance in the eyes of the owners into a real obstacle for driving the things, thus putting an end to perhaps the most obnoxious aspect of bourgeois carbon addiction," the group said in a statement.
Police received a number of complaints on Tuesday from vehicle owners in the Fredhäll area of Stockholm.
"We are encouraging car owners to be on their guard. In a number of cases they have failed to notice the sabotage before driving off in their vehicles, thereby putting themselves and others in danger," said police commissioner Johan Lindborg.
SUV owners in Stockholm are not the only ones who need to stay on the alert, as new "tribes" have also emerged in Gothenburg, Malmö and Sundsvall.
Every time The Indians of the Concrete Jungle sabotage an SUV, they also leave a note for the owners explaining the potentially devastating effects of climate change.
"This does not have to happen if we impose a radical cut on carbon emissions. Now.
Not tomorrow. That's why we have disarmed your SUV by deflating the tires," they write.
But the Indians' methods have not gone unchallenged. During the autumn the similarly anonymous Cowboys of the Concrete Jungle set up a website using the same design as their environmentalist foes.
"There are many of us who view their methods with disgust, and if the Sheriffs of The Concrete Jungle (the police) can't manage to get to grips with them, we will continue to organize in order to protect our rights and our property," they wrote.
The Cowboys added that they were in the process of creating a network around the country with plans to infiltrate the activist group and reveal the identities of its members.