“A Swedish citizen – a man in his thirties – was detained in Iran in April 2022. The Ministry for Foreign Affairs and the Embassy of Sweden in Tehran are working very intensively on the case and are maintaining close contact with the EU,” Sweden’s foreign ministry told AFP in an e-mail.

“The Swedish citizen has been arbitrarily deprived of his freedom and should therefore be released immediately.”

The ministry added it was in daily contact with the detained man’s family.

The New York Times has named the man as Johan Floderus, a 33-year-old who works for the EU’s diplomatic service. He was arrested on April 17th last year as he returned to Tehran following a holiday.

Neither the Swedish authorities nor the European Union have confirmed the detainee’s identity, although his family said in a statement sent to public broadcaster SVT, among others, that they were “deeply worried and devastated”.

“Johan was suddenly and for no reason at all taken into custody while on a holiday trip and has been in an Iranian jail for more than 500 days. We know that many are working hard to free him and we are grateful for that,” they said.

Iran announced in July last year it had arrested a man on suspicion of espionage.

“We are aware and have been following very closely the case of a Swedish national detained in Iran,” a European Commission spokesman said.

“We are in a very close touch with the Swedish authorities who have the consular responsibility,” the spokesman added.

“This case has also to be seen in the context of the growing number of arbitrary detentions involving EU citizens,” the Commission spokesman added.

“We have used and will continue to use every opportunity to raise the issue with the Iranian authorities to achieve – in close cooperation with the member states involved – the release of all arbitrarily detained EU citizens.”

The announcement of his arrest in July 2022 came two weeks after an Iranian citizen received a life jail term in Sweden for his role in the Iranian regime’s 1988 mass executions of thousands of opponents.

A Stockholm court found former Iranian prison head Hamid Noury guilty of “aggravated crimes against international law” and “murder”.

Several Western states have denounced what they term “hostage diplomacy” on the part of Iran, consisting of arresting Western nationals to obtain concessions such as the release of its own nationals.

Last May, Belgian humanitarian worker Olivier Vandecasteele, 42, was released after 15 months in Iranian detention for alleged spying in a prisoner swap for Iranian diplomat Assadollah Assadi, sentenced to 20 years for plotting to bomb an opposition rally in Paris.