Iran's security service was behind a special operation against targets in Sweden, the Nordic country's Prosecutor's Office said.
The operation saw hackers send thousands of text messages to Swedes calling for revenge over 2023 burnings of the Koran, according to the Prosecutor's Office.
Senior prosecutor Mats Ljungqvist said in a statement on September 24 that a preliminary investigation showed "it was the Iranian state via the Iranian Islamic Revolutionary Guards Corps (IRGC), that carried out a data breach at a Swedish company that runs a major SMS service."
He added that investigators were able to establish the identities of the Iranian hackers who carried out the data breach.
"The aim was to further tighten the situation and increase the conflict that prevailed between different groups in society," Ljungqvist said, adding that while the conditions for prosecution abroad or extradition to Sweden "are lacking" for those suspected of being behind the breach, the case can be reopened.
It "does not mean that the suspected hackers have been completely written off. As long as the crime is not time-barred, prosecutors can open the preliminary investigation again," Ljungqvist said.
The Iranian Embassy in Stockholm said that the accusations and the act of publishing them "poison and affect the atmosphere of bilateral relations."
The embassy "considers the accusations to be baseless and rejects them," Iran's Tasnim news agency quoted the embassy as saying.
Sweden last summer saw a series of Koran burnings that sparked massive unrest and strained relations between Stockholm and several Middle Eastern countries.
While the Swedish government officially condemned the burnings of a book Muslims consider as the sacred word of God, lawmakers also said they could not stop the actions as they were protected by freedom of speech and assembly laws.
The issue also delayed Sweden's entry to NATO as Turkey raised objections saying it was "unacceptable to allow anti-Islam protests in the name of freedom of expression."
Swedish prosecutors said a group calling itself the Anzu team was the sender of the 15,000 text messages sent to Swedes that called for revenge against Koran burners.
They did not identify the Swedish company that runs the SMS text service.