The Omani Foreign Ministry announced, in a statement posted on Twitter, that prisoners from both Tehran and Brussels were transported to Muscat, where they will be swapped to be returned to their respective home countries. 

#Statement | In compliance with the directives of His Majesty Sultan Haitham bin Tarik, to fulfill the requests of the Iranian and Belgian governments to assist in resolving the issue of detained citizens in both countries, the Omani efforts have resulted in an agreement, pic.twitter.com/QgHPHm1R1f

— وزارة الخارجية (@FMofOman) May 26, 2023

The statement added that the Sultanate of Oman appreciated the high positive spirit that prevailed in the talks in Muscat between the Iranian and Belgian sides, and their keenness to settle this humanitarian issue.

Check out: EU prisons deny an Iranian diplomat basic human rights

The prisoner exchange treaty with Belgium was ratified by President Ibrahim Raisi in November last year. 

The Belgian House of Representatives approved the treaty on July 2022, but an Antwerp court froze, two days later, any possibility to extradite diplomat Asadollah Assadi, whom Antwerp sentenced to 20 years in prison, to Iran.

An Antwerp court convicted Assadi of allegedly supplying explosives for a thwarted 2018 bomb plot that attempted to target the MEK terror group in a rally outside Paris, France.

Tehran has demanded that Belgium recognize Assadi's diplomatic status and release him, while Belgium argued that Assadi's diplomatic status did not grant him protection from the charges brought up against him. 

It is noteworthy that former Iranian Foreign Minister Mohammad Javad Zarif condemned Assadi's arrest at the time, saying it was peculiar that such a thing would take place during a visit by the Iranian President to Europe, hinting at foul play.