Belgium PM tells Iranian leader to free aid worker

Belgian Prime Minister Alexander De Croo on Wednesday urged Iran's president to "immediately" set free an aid worker held by Tehran in a case denounced as hostage diplomacy.

Iran arrested Olivier Vandecasteele, 42, in February 2022 and sentenced him at the start of this year to more than 12 years behind bars for "espionage" as well as ordering him to be subjected to 74 lashes.

"My message was very clear: Olivier Vandecasteele is an innocent man and must be released immediately," De Croo tweeted after a phone call with Iran's Ebrahim Raisi.

"In the meantime, his inhumane prison conditions must change."

UN rights experts have slammed Vandecasteele's detention as a "flagrant violation" of international law.

His backers and rights groups say he is being held as part of Iran's "hostage diplomacy" to try to get Belgium to release an Iranian diplomat incarcerated for terrorism.

The diplomat, Assadollah Assadi, was found guilty in 2021 of masterminding a plot to blow up an event organised by an Iranian exiled opposition group outside Paris in 2018.

The plot was foiled by European intelligence services, and Assadi, a diplomat stationed in Austria who was identified as having provided the explosives for the bomb, was sentenced to 20 years in prison.

In July last year, Belgium and Iran signed a prisoner-swap treaty that Brussels viewed as a path to free Vandecasteele.

But Belgium's Constitutional Court suspended the treaty after exiled Iranian opposition members challenged it on the grounds it would lead to the release of Assadi.

The court is set to rule on the legality of the treaty by March 8.