The Scandinavian country's security, which had already deteriorated after Russia's invasion of Ukraine, has worsened since the US-Israeli strikes on Iran on Saturday unleashed a new war, according to Fredrik Hallstrom, head of operations for the Swedish Security Service (Sapo).

"The threat has increased primarily against American, Jewish, Israeli interests or opposition figures, rather than towards Sweden as a nation or country," Hallstrom told AFP.

"I'm talking about opposition figures with such influence that they could actually either be perceived as a serious threat to the Iranian regime, or in fact be one," he explained.

Hallstrom also said the war in the Middle East could have "considerable impact" on European security.

Police have taken measures to increase security around potential targets, such as embassies, he said.

Sapo has previously pointed to Iran, China and Russia as the main threats to the country.

It has accused Iran in particular of recruiting members of Swedish criminal gangs to commit "acts of violence" against Israeli and other interests in Sweden -- a claim Iran denied.

Other risks highlighted by Sapo include increased intelligence activities in Sweden, surveillance and actions targeting Iranian dissidents in exile, as well as the acquisition of equipment, research and know-how that could contribute to the development of nuclear weapons.

"We know that Iran uses cyber attacks and hacks phones and computers in order to monitor others," Hallstrom said.

He added that this monitoring could be potentially used to get individuals "in Sweden to provide information about other people, by exerting pressure".