Stockholm's bomb squad eventually detonated the object and there were no injuries or damage to the building. The Swedish prime minister later called the incident "an attempted attack".

"The criminal classification for the suspected crime is changed to terrorist crime due to grossly illegal threats and attempts to cause public destruction," said the security police, which has now assumed responsibility for the investigation.

(Reporting by Essi Lehto, editing by Stine Jacobsen and Terje Solsvik)