Police in the southern Swedish city of Malmo said about 15 people were briefly detained following unrest late Friday, triggered by an illegal protest where a copy of the Koran was kicked.
The unrest was additionally fuelled by reports that a Koran was later burned in a part of the mainly immigrant district of Rosengard.
About 300 people assembled and threw stones at police and rescue services, while cars and tyres were set ablaze.
Police said they had restored order early Saturday.
A Danish anti-Islamic politician, Rasmus Paludan, was earlier Friday stopped at the Swedish-Danish border and subsequently banned from entering Sweden for two years.
Paludan had been invited to a protest organized by an anti-Islamic group. Their plan was reportedly to burn a Koran wrapped in bacon, a stunt that had reportedly been staged earlier in Denmark.
Malmo police earlier this week denied permission for the anti-Islamic protest at the central Stortorget square in Malmo, a decision later upheld by a court.
Some supporters of Paludan assembled on the square and images on social media showed a copy of the Koran being kicked.
Police broke up the gathering and detained six people on suspicion of incitement against an ethnic group.
Stefan Sinteus, Malmo police chief, said it was deplorable that the protesters in Rosengard vented their anger at the authorities, although police understood the anger triggered by the burning of the Koran.
Police were investigating the incidents and working with religious groups, other organizations and local authorities to ensure people felt safe, he said.
Paludan was in June sentenced to a three-month prison sentence in Denmark over various violations of that country's hate-speech laws.