Emergency crews are at the site of an explosion in an apartment in a residential area of Malmo, Sweden's third largest city.

Local media reports say a blast occurred at around 10pm local time shattering windows. It is unclear if anyone was inside.

There was a report someone had beaten down a door and thrown an explosive device inside, regional daily Sydsvenska Dagbladet said.

According to The Expressen, surrounding streets have been blocked.

Residents had been told to stay indoors while the bomb squad worked to clear the area. Initial reports were of no injuries.

The publication quoted police spokeswoman Anna Goransson as saying the cause of the blast was yet unknown.

The streets were reopened shortly after midnight, it said.

On Tuesday, an unidentified assailant shot and wounded a man in a shopping mall in Malmo, but police said the attack had nothing to do with recent Islamist militant violence elsewhere in Europe.

A Malmo police statement said the victim was shot in the leg and taken to a local hospital.

A police spokesperson later told Sydsvenska Dagbladet that the incident, in a mainly immigrant neighbourhood of Sweden's third largest city, was being investigated as a case of aggravated assault or attempted murder, and had no connection with Islamist militancy.

Europe has been shaken by a series of violent attacks on civilians in Germany, France and Belgium over the past 18 months.

More to come

- Brisbane Times with Reuters