The act is currently being investigated as a hate crime and incitement against an ethnic group, the police said, Sputnik reported.
The installation was found in a parking lot in a residential area. By the time the police patrol arrived at the scene, many onlookers had already gathered to get a glimpse.
“Many people were very upset when we arrived at the scene,” police press spokesperson Björn Öberg told the newspaper Dagens Nyheter.
According to Öberg, law enforcement officers took the Quran back to the station to help in the investigation, but they discarded the boar head as rubbish because it was impossible to find any fingerprints or other helpful information on it.
No one at the scene saw any suspects who could possibly be linked to the incident, according to the police, who have no suspects and asked citizens in possession of any related information to contact the authorities.
Vetlanda, an industrial town of 12,500, is the seat of the eponymous municipality in Jönköping County.