"It is very serious," Löfven told reporters. "It is not the Sweden we want to see."
He spoke just hours after the latest attack on housing for asylum seekers in normally tranquil Munkedal, a town of 10,000 inhabitants in south-western Sweden.
Emergency services were called to the building for asylum seekers just after 4am, with firefighters still working to put out the blaze five hours later. No one was seriously injured, although some of the 14 migrants living there suffered slight smoke inhalation. They were swiftly rehoused.
"I thought I was going to die. It was horrible, but now it's okay, I'm safe," said Ahmet, a Somalian refugee interviewed by Swedish public radio.
Officers around the country are still investigating a separate suspicious fire at an old school building earmarked for asylum accommodation in Onsala south of Gothenburg over the weekend, just days after another two hubs were burned to the ground in Ljungby and Arlöv in southern Sweden.
More than a dozen fires at housing for refugees have been reported in 2015, the majority of which are understood to have been started deliberately.
A spokesperson for the Swedish Civil Contingencies Agency (MSB), which has been tasked with erecting a tent camp for 375 refugees at Revinge in southern Sweden, told The Local that they were in close contact with police authorities to prevent similar attacks.
"We are looking at it in general as well as [the Revinge tent camp] in particular, where we will have plenty of staff on site, to make sure we are taking necessary precautions," said head of coordination Anna Nyman.
The agency had previously said the tents could be set up as early as this week, but Nyman told The Local on Tuesday that they would be submitting the application for planning permission on Wednesday.
Lund Council, which is the local authority in charge of the area, told the TT newswire that they would prioritize the application, but that it could still take a couple of weeks before it is approved or rejected.
The heated tents that are set to be put up in Revinge. Photo: MSB
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Meanwhile, Umeå municipality in northern Sweden announced on Monday that it was not planning to disclose where it was set to house 150 asylum seekers out of fear of arson attacks.
"After the past week's fire incidents in southern Sweden I don't think it's okay to expose the addresses. The risk is that thugs decide to burn down the premises here as well," Ewa Klingfors, director of Umeå council's social services, told Västerbottens-kuriren.
With Sweden taking in record number of refugees, Sweden's Migration Agency (Migrationsverket) recently sent out a nationwide appeal for local councils and businesses to provide shelter as winter sets in.
A total of 95,430 people have already launched asylum cases so far in 2015, according to Migrationsverket.