Sweden’s prime minister has promised to “go in hard” against masked men who set alight up to 80 cars in Gothenburg and other towns on Sweden’s west coast, in what police say appeared to be coordinated attacks.

“I am really furious, what the hell are they up to?” Stefan Löfven told Swedish radio on Tuesday morning. “Society will always act hard against this and we must continue to do so … We will do what needs to be done to take care of it and go in hard against this crime.”

Sweden goes to the polls on 9 September with violent crime high on the political agenda after a spate of shootings and grenade attacks, largely in deprived areas with large concentrations of immigrants.

Opposition leaders have accused the ruling centre-left coalition of allowing “no-go zones” to emerge where emergency services fear to tread.

Clouds of dense black smoke billowed around high-rise apartment blocks in a shopping precinct in Frölunda, western Gothenburg, as cars burned shortly before dusk on Monday. Just after 9pm, small groups of masked youths wearing black had set light to about 60 cars in the city.

In Trollhättan, 45 miles (70km) to the north, police said between 30 and 40 young people threw stones at officers and set fire to cars, tyres and wooden pallets. Vehicles were also torched in several nearby towns. In total, about 100 cars were damaged.

Police made two arrests on Tuesday afternoon and said they were hunting more suspects.

On Tuesday evening police said they suspected a link between Monday night’s unrest in the Gothenburg area and the large number of arrests of criminal gang members in the city during the summer.

The coordinated nature of the attacks made some suspect an attempt by the far right to whip up anti-immigrant sentiment ahead of the election, in which the anti-immigrant Sweden Democrats are vying to become the country’s largest political party.

Daniel Riazat, an MP for the Left party, said on Twitter: “I would not be surprised if far right extremists were involved in some way.”

In recent years there has been a pattern of young people setting fire to cars a week or 10 days before the start of school, police said. Schools return in Gothenburg on 20 August.

“[But] this is much much bigger than it used to be, much more serious,” a police spokesperson told Swedish media. It was unprecedented to have so many incidents at the same time in different places, they said, adding that the events appeared to have been coordinated via social media.

Emergency services extinguished the Gothenburg fires by about 1am. Nobody was injured and there were no arrests. Police said there were no unusual incidents in Stockholm, the capital.

An investigation last month by the liberal daily newspaper Dagens Nyheter found no parts of Sweden where emergency services, postal workers or parking wardens were regularly unable to carry out their work, although threatening situations sometimes arose.

Arson attacks on cars and schools in Stockholm in May 2013 were fuelled by anger among second-generation immigrants at their perceived second-class status in Swedish society. There was also a wave of car burnings in several Swedish towns in 2016, but recent concerns have focused on deadly shootings and grenade attacks among drug gangs.

Ulf Kristersson, the leader of the centre-right opposition, said on Tuesday: “Sweden has tolerated this for too long. Now it just has to stop.”

In a message to the arsonists, Löfven said: “You destroy it for yourself. You destroy it for your parents, you destroy it for entire neighbourhoods, for your neighbours, and society must respond very hard.”