The family of a Swedish EU employee detained in Iran has urged the international community to help secure his release.

"The family, friends, and supporters of Johan are calling for urgent international attention to secure his immediate release and safe return to Europe," Johan Floderus' family wrote on a website dedicated to his release, on his 33rd birthday, on Sunday.

The European Union's top diplomat Josep Borrell said on Tuesday that Floderus' case had been raised repeatedly with authorities in the Islamic Republic.

His family said Floderus was being held more than 500 days for alleged spying without formal charges at Tehran's Evin prison, where political prisoners and many detainees facing security charges, including Iranians with dual nationality, are jailed.

His family said Floderus had travelled throughout the Middle East to study languages, explore historic sites and to support humanitarian cooperation projects in Iran on behalf of the EU, and was arrested in April 2022 before leaving the country.

"His needs for adequate food rations, outside walks, medical checkups and much more are not respected (in jail)," they said, adding that he had been denied "communicating" with Sweden's embassy in Tehran, except a few consular visits.

They said that starting in February 2023 Floderus was restricted to making short phone calls once a month. "He had to go on hunger strike to be allowed to make several of these calls, which have to be in English and monitored."

(With reporting by Reuters)