A member of Kasselia's congregation, 29-year-old Salim Iskef, was among those murdered in Orebro on Tuesday in Sweden's first school shooting and the worst mass shooting in the country's history. The gunman killed 10 students at an adult learning centre and then himself.

Salim Iskef, 29, fled the Islamic State and Syria to form a better, more secure life in Sweden, only to be gunned down this week in the worst mass-shooting in Swedish history.

The police responding to the attack encountered firing so intense that they struggled to tell how many gunmen were on the scene, an official said.

One person died after a shooting in Brussels that was likely linked to clashes between rival drug gangs, the local prosecutor's office said on Friday, highlighting rising crime in the Belgian capital city which also hosts the main EU institutions.

The authorities said no injuries had been reported, but two metro stations were closed on Wednesday after the shooting.