Up to 80 cars were set on fire overnight across western Sweden by masked vandals, police said on Tuesday, in what they suspect was a coordinated attack weeks before a general election.

Most of the cars were burned at around 20 locations in Sweden's second largest city of Gothenburg late on Monday.

Authorities said two suspects aged between 16 and 21 have been arrested so far in Gothenburg and would be questioned on Tuesday.

Police said they believe the attacks were organised on social media. No one was injured in the car blazes.

“We've never seen this many cars set on fire before,” Hans Lippens, police spokesman in western Sweden, told AFP.

The incident triggered outrage among Swedish politicians who are busy campaigning for the September 9 general election.

“I'm furious. My question to (the perpetrators) is: what the hell are you doing?” Social Democratic Prime Minister Stefan Lofven told public broadcaster Swedish Radio on Tuesday.

“You're ruining things for yourselves, your parents and your neighbourhoods,” Lofven said, adding the incident “looked very coordinated, almost like a military operation”.

Cars set ablaze is common in Sweden. In Stockholm's suburbs alone, such crimes happen almost on a daily basis, usually attributed to disadvantaged youths.

Last year, 1,457 cars were “deliberately” set on fire across Sweden, compared to 1,641 in 2016, according to the Swedish Civil Contingencies Agency's figures.

“Sweden has tolerated this for too long. This must end now,” Ulf Kristersson, leader of the conservative opposition party, the Moderates, wrote on his Facebook account.

Last year in February, two days after US President Donald Trump's baffling comments linking crime to immigration in Sweden, riots broke out in the immigrant-heavy northern Stockholm suburb of Rinkeby.

Dozens of youths clashed with police after they arrested a suspected drug dealer in Rinkeby. The rioters threw stones at police, burned cars and looted shops.