Sweden's foreign ministry has summoned Iran's charge d'affaires, urging the immediate release of Swedish citizens held in Iran under “arbitrary detention”.

"Sweden's demands for the immediate release of the Swedish citizens arbitrarily detained in Iran, consular access to detained citizens and respect for international commitments on consular matters were stressed at the meeting," Sweden's Ministry for Foreign Affairs said in a statement.

"The government has heard reports of further arrests of Swedish citizens," it added.

"In late 2023, a man with Swedish and Iranian citizenship was detained for no apparent reason," it continued, without adding further details.

The ongoing diplomatic strain between Sweden and Iran intensified following a recent court decision in Sweden to sentence Hamid Nouri, a former Iranian prison official, to life imprisonment. Noury was found guilty of "grave breaches of international humanitarian law and murder" related to mass executions in 1988, resulting in the deaths of more than 5,000 prisoners.

Tensions escalated with the Swedish appeals court's confirmation of Nouri's life sentence on December 19. In response, Iran summoned Sweden's charge d'affaires to protest the verdict.

In December, the trial began of Sweden's EU diplomat, Johan Floderus, on charges of conspiring with Israel, Iran's arch-enemy. Floderus had been arrested in April 2022 at Tehran airport upon his return from a trip with friends.

EU chief Josep Borrell said at the time: "As [the] EU, we have been very clear from the beginning: Mr. Floderus is innocent. There are absolutely no grounds for keeping Johan Floderus in detention."

Last year, Iranian-Swedish dissident Habib Chaab was executed on charges of "corruption on earth." Iranian-Swedish academic Ahmadreza Djalali was sentenced to death in 2016 on espionage charges.