A gang of masked “youths” rampaged through Sweden’s second-largest city Monday night, setting cars ablaze in an attack described as “extremely organised” and like a military operation by the Prime Minister.

Shocking video of fire engulfing numerous vehicles in Gothenburg spread on social media Monday evening with other footage clearly showing masked people in dark clothing intentionally lighting the blazes.

Police chose not to arrest the “young people” at the scene and have since contacted their parents, reports state.

Officers said Tuesday that up to 100 cars had been either burnt to or vandalized in the city and in nearby towns such as Trollhattan, an industrial area with high unemployment, and Falkenberg.

Falkenberg contains gender-segregated asylum seeker homes and police have been repeatedly attacked en mass in nearby Trollhattan, with well knows Islamic State fighters hailing from the area.

Such areas, with large migrant populations, have become hotspots for violence in the Nordic nation in recent years with many described as “no-go zones.”

Fires were also reported on a smaller scale in Malmo, Sweden’s third largest city.

Sweden is to hold national elections in less than a month, and left-wing Prime Minister Stefan Löfven reacted angrily to the latest attacks, blasting the perpetrators directly.

“I’m getting pissed off – really! My question to these people is what the hell are you doing?” he said on a radio show according to Aftonbladet, promising to push for harsher penalties against those involved.

“It seems very organized, almost like a military operation,” he said, adding: “My message to those involved is that there is no disappointment, frustration, or injustice that motivates you to turn on someone else’s car.”

“We have summed up the damage in all the different places. It’s a total of about 100 cars that are damaged or burned out,” police spokesman Ulla Brehm told SVT.

She added: “We have already started talking to parents of the young people who were active in the morning. We chose not to seize someone on the spot but have identified them, and talked with them.”

Witnesses told Swedish news agency TT they had seen “masked youths” fleeing the scene. No injuries have been reported and no arrest made, according to local reports.