Police said they fired warning shots during a riot to disperse protesters angry about demonstrations over the past several days by a Danish anti-Islam group in Sweden.
Three people were slightly injured during the clashes.
A crowd of about 150 people threw stones at officers and police vehicles, and set fire to cars.
Police said they responded by firing warning shots and “three people seem to have been hit by ricochets” and were taken to hospital in Norrkoping, which has around 130,000 residents and is about 100 miles south west of Stockholm.
“All three injured are arrested on suspicion of crime,” police said, adding that none of them had serious injuries.
A photographer for Swedish news agency TT at the scene reported that several riot police officers were seen carrying a wounded man to an ambulance.
The riot broke out following Danish far-right politician Rasmus Paludan’s meetings and planned Koran burnings in various Swedish cities and towns since Thursday.
Mr Paludan and his Stram Kurs party had planned a demonstration in Norrkoping on Sunday but he never showed up in the city, Swedish media reported. Unrest was also reported in the nearby city of Linkoping.
Mr Paludan said on the party’s Facebook page that he decided to cancel Sunday’s demonstrations in the two locations as the Swedish authorities in the region have “shown that they are completely incapable of protecting themselves and me. If I was seriously injured or killed due to the inadequacy of the police authority, then it would be very sad for Swedes, Danes and other northerners”.
Apart from Norrkoping and Linkoping, unrest and violent clashes have been reported in Stockholm, Orebro, Landskrona and Malmo – Sweden’s third-largest city, in the past three days.
On Friday evening, violent clashes between demonstrators and counter-protesters erupted in the central city of Orebro before Mr Paludan’s plan to burn a Koran there, leaving 12 police officers injured and four police vehicles set ablaze.
In Landskrona, southern Sweden, a few hundred mostly young people threw stones and set cars, tyres and dustbins on fire. They also erected a barrier fence that obstructed traffic on Saturday evening. Similar unrest took place in nearby Malmo, where a city bus was set on fire, among other things, late on Saturday.
Mr Paludan, a Danish lawyer who also holds Swedish citizenship, set up Stram Kurs, or “Hard Line” in 2017. The website of the party, which runs on an anti-immigration and anti-Islam agenda, says “Stram Kurs is the most patriotic political party in Denmark”.
