Gothenburg police and fire services were alerted to the first blaze after 9pm, after which several more calls came in from the city as well as Trollhättan, Lysekil and Falkenberg some 100 kilometres away.
"We have been to around 20 places in Gothenburg. It's mainly vehicles that have burned – cars, some truck, caravans – but also some buried waste disposal site," Johan Eklund, emergency control room officer in the greater Gothenburg area, told Swedish news agency TT shortly after midnight.
Swedish media reported that groups of up to ten youths had been seen throwing stones and lighting cars on fire in Gothenburg districts Gårdsten, Hjällbo and Frölunda, among other locations.
Videos posted on social media showed masked people dressed in black torching cars.
In Trollhättan, 70 kilometres north of Gothenburg, a larger group of people was reportedly involved, wrote TT. Six cars burned in the town and youths were reported throwing stones at police.
"We know from experience that these kinds of fires more often happen the week before schools start than other weeks," police spokesperson Ulla Brehm told TT.
Gothenburg police said on Monday morning they believed the attacks had been coordinated on social media, but added that they were still investigating and were not yet able to confirm that that was the case.
In total around 80 cars were set on fire across the region, said Gothenburg police.
No arrests had been made as of 10am, but police said they had manage to identify several people believed to be involved.
Car burnings were also reported to a smaller extent in Malmö and Helsingborg. Southern police spokesperson Fredrik Bratt told TT it was "not completely out of the ordinary" and added he did not believe they were linked to the Gothenburg fires, but said they were monitoring the situation.
Around a dozen cars also burned in Stockholm, Uppsala and Åkersberga on Monday night, wrote the Expressen tabloid. There were no other reports of riots or violence in those areas, it added.