Police investigating Sweden's worst mass shooting were still trying to establish a motive as to why a lone gunman opened fire at an education campus in the southern city of Orebro, killing 10 people.

About 10 people, including the gunman, were killed on Tuesday at an adult education center in what Sweden’s prime minister called the country’s worst mass shooting. But a final death toll, a conclusive number of wounded and a motive hadn’t yet been determined hours later.

Police in Sweden said "about 10" people were killed in a shooting at an adult education school . The shooting occurred at Campus Risbergska in Örebro, Sweden, the city said in a statement. Police say the shooter is believed to have been killed.

Police say around 10 people have been killed in a shooting at an education centre in central Sweden, including the suspected gunman. Prime Minister Ulf Kristersson described Tuesday's attack at Risbergska school in Orebro,

Sweden’s worst mass shooting has left at least 11 people dead, including the gunman, at an adult education center as officials warned that the death toll could rise.