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.

Swedish police said on Wednesday that "erroneous narratives" were being spread on social media regarding the mass shooting on Tuesday at an adult education centre, the Nordic country's deadliest gun attack.

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,