The attack on Tuesday - described by Sweden's prime minister as the "worst mass shooting" in the country's history - happened at a school for adults.

Around 10 people were killed in a school shooting in Örebro. The damage at the crime scene was so extensive that investigators were unable to be more definitive, said Roberto Eid Forest, head of the local police.

Swedish Prime Minister Ulf Kristersson and King Carl XVI Gustav have led tributes to the victims of a deadly shooting at an adult school in the city of Orebro. A police investigation is underway.