At least four people have been transported to nearby hospitals but the nature of their injuries remains unclear, according to a Swedish police report.
"A major police operation is underway".
Trelleborg, known for its past gang violence, is located 33 kilometres south of Malmo and 64kms southeast of Copenhagen, Denmark.
"There were many shots".
Shortly thereafter, armed police arrived and cordoned off the crime scene, where witnesses had reported hearing a loud "bang".
"When we get there we found several people who were injured in a few different places".
"It's packed with police cars in the street".
An eyewitness to Swedish official news agency, TT, said he heard six gunshots and saw many people fleeing environment.
He added: "Right now, it's blocked off".
Residents of Trelleborg, a town of some 40,000 people, told local media that "There were many shots".
'We are blocking certain areas and will conduct an investigation.