COPENHAGEN, Denmark (AP) — Swedish Prime Minister Stefan Lofven is lashing out at those who set fire to dozens of cars in southwest Sweden, asking them "what the heck are you doing?"

Lofven says in a Swedish radio interview that he is "really getting mad," adding that "the society must react in a tough manner."

Police spokesman Hans Lippens said Tuesday that initial reports indicate that about 80 cars were set ablaze overnight, chiefly in Sweden's second largest Goteborg and nearby Trollhattan, an industrial city.

Lippens added that because the fires started within a short period of time, "we cannot exclude that there is a connection between the blazes."

No injuries have been reported. However, the fires tie up police and rescue officials and frighten residents.

The reason for the fires was unknown.