Clashes have erupted in an immigrant neighbourhood in Sweden’s third largest city after an anti-Muslim protester set fire to the Koran, police have said.

Police in Malmo said they were pelted with rocks and dozens of cars were set on fire, including in an underground garage, describing the events that started on Sunday and lasted overnight as “a riot”.

The clashes started after an anti-Islam activist Salwan Momika burned a copy of the Koran and an angry mob tried to stop him while police, some of them in riot gear, detained at least three people.

Early on Monday, an angry crowd of mainly young people also set fire to tyres and debris, and some were seen throwing electric scooters, bicycles and barriers in Malmo’s Rosengard neighbourhood, which has seen similar clashes in the past. There were several banners relating to the Koran burning.

Senior police officer Petra Stenkula said: “I understand that a public gathering like this arouses strong emotions, but we cannot tolerate disturbances and violent expressions like those we saw on Sunday afternoon.

“It is extremely regrettable to once again see violence and vandalism at Rosengard.”

Speaking at a news conference, Swedish Prime Minister Ulf Kristersson said: “Regardless of the reason behind these riots, the car fires, the harassment, violence against police officers… regardless of the reason, I think that all Swedes find this completely unacceptable.”

In the past months, Mr Momika, a refugee from Iraq, has desecrated the Koran in a series of anti-Islam protests mostly in Stockholm that have caused anger in many Muslim countries. Swedish police have allowed his actions, citing freedom of speech.

The Koran burnings have sparked angry protests in Muslim countries, attacks on Swedish diplomatic missions and threats from Islamic extremists. Muslim leaders in Sweden have called on the government to find ways to stop the Koran burnings.

Sweden dropped its last blasphemy laws in the 1970s and the government has said it has no intention to reintroduce them.

However, the government has announced an inquiry into legal possibilities for enabling police to reject permits for demonstrations over national security concerns.

Read more: Koran burned again in Sweden as government considers ban

Two men in Sweden took part in a demonstration that involved burning a Koran outside a mosque in the centre of the capital Stockholm on Wednesday.

Sweden’s Prime Minister Ulf Kristersson said at a press conference that the action – taking place on the Islamic holiday of Eid al-Adha – was permitted, but not appropriate.

Footage from Swedish broadcaster SVT showed a man setting fire to a copy of Islam’s holy scripture behind police cordon tape. Apparently, only one other man took part in the demonstration. Dozens of people gathered behind the cordons, some shouting angry words.

According to the media reports, the public demonstration remained calm. One person who was holding a stone was led away from the site, according to the report.

The Stockholm police had previously given the green light for the small protest. According to the application, seen by the dpa, only two people were expected to attend the demonstration.

Swedish authorities authorized the protest because Swedish courts had ruled that police did not have the right to refuse permission for Koran burnings.

In February, the police refused the request of two organizers to conduct Koran burnings in Stockholm for security reasons.

Islamophobic protests have caused considerable trouble between Sweden and Turkey in recent months.

It is unclear if Wednesday’s Koran burning will cause new problems for Swedish-Turkish relations.

This incident could pose a serious problem for Sweden’s NATO membership application, which they submitted more than a year ago. It is still blocked by Turkey and Hungary. New members must be approved unanimously by all existing NATO members.

Turkish President Recep Tayyip Erdoğan has repeatedly accused Sweden of not taking action against “terrorist organizations,” an apparent reference to mostly Kurdish political groups from Turkey that operate in exile in the country such as the banned Kurdish Workers’ Party (PKK).

Sweden has recently tightened its terrorism laws and the country’s supreme court approved the first extradition to Turkey of an alleged PKK supporter.

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