Washington: In the Swedish city of Gothenburg on Monday night, plumes of smoke rose above the shells of burnt cars as fire engines raced to put out a string of blazes that were captured on camera.

More than 100 cars were "burnt or damaged" in and around the nation's second-largest city, police spokeswoman Ulla Brehm said, after youths reportedly moved through the area torching passenger vehicles.

"They were organised and prepared," Brehm said, according to Reuters. No injuries were reported, but photos show that many cars were destroyed. On Tuesday, police said they had arrested a 16-year-old and 21-year-old in relation to Monday's attacks, and planned to detain more suspects during the day.

Prime Minister Stefan Lofven said on Swedish radio that the fires appeared to be "very organised, almost like a military operation".