Sweden's Foreign Ministry confirmed on Monday that a man in his twenties was arrested in Iran this month and is being held in custody.
The Swedish man "was detained in Iran in early January", the ministry told AFP.
"The embassy in Tehran is in contact with local authorities. The Ministry of Foreign Affairs is in contact with relatives in Sweden," it said.
The man lived in central Sweden, according to the Foreign Ministry, which said it could not give any more details because of "consular confidentiality".
On December 19, a Swedish appeals court confirmed a life sentence for the former Iranian prison official, Hamid Noury.
Noury, 62, was convicted of "grave breaches of international humanitarian law and murder" over his role in a purge in which at least 5,000 prisoners killed in Iran in 1988.
The next day, Iran summoned Sweden's charge d'affaires to protest the sentence.
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In December, Swedish EU diplomat Johan Floderus went on trial in Iran on charges of conspiring with Iran's arch-enemy Israel.
Floderus, 33, was arrested on April 17, 2022, at Tehran airport as he was returning from a trip with friends.
His arrest came while Noury was being tried in Sweden, which led to a life sentence handed down in July 2022. The verdict was appealed.
Swedish Prime Minister Ulf Kristersson demanded the immediate release of Floderus on December 11 last year.
Iran has previously used detained foreigners as bargaining chips to secure the release of its citizens abroad, and Swedish media reports have also speculated about the possibility of a prisoner swap.
In May 2023, the Iranian-Swedish dissident Habib Chaab was executed after a conviction of "corruption on earth".
