The Belgium-born NGO worker had been sentenced to a total of 40 years in prison in Teheran for widely contested charges of "espionage."
Olivier Vandecasteele, the Belgian humanitarian aid worker imprisoned in Teheran since February 2022 under criminal charges widely contested, has been released from jail and is currently heading back to his home country.
The news was announced by Belgian Prime Minister Alexander De Croo in a press release released on Friday morning.
"Olivier Vandecasteele is on his way to Belgium. If everything goes as planned, he will be with us tonight. Finally free", De Croo wrote.
"Oliver spent 455 days in a Teheran prison. In unbearable conditions. Innocent."
His return is "a relief for his family, for his friends, for his colleague," De Croo added, later tweeting a picture of the NGO worker onboard a plane, writing "At last with us".
Vandecasteele left Teheran on Thursday night and was flown to Oman to undergo a medical examination, the prime minister said. The worker was accompanied by Belgian diplomats and military officers.
His release was made possible after a prisoner swap between Iran and Belgium, the Omani foreign affairs ministry said in a statement.
The Belgian government had previously tabled a controversial treaty on prisoner exchanges in a bid to secure the release of the 42-year-old.
Shortly after De Croo's announcement, the Iranian government confirmed the exchanged prisoner was Assadollah Assadi, an Iranian national who had been sentenced to 20 years in prison by a court in Antwerp in 2021 for plotting a failed bomb attack against an Iranian opposition group in Paris.
NGO Médecins du Monde, with which Vandecasteele worked, said it learned of his release "with immense relief".
"We wish him a safe journey home and a happy stay with his loved ones," it added.
Who is Olivier Vandecasteele?
Born in Tournai, a French-speaking city in southern Belgium, Vandecasteele spent his professional career working for several humanitarian NGOs in countries such as Afghanistan, Mali, the Sahel region and, most recently, Iran.
The Belgian national returned to Iran in February 2022 to pick up his personal affairs in what was supposed to be a quick trip before definitely leaving the country.
But his departure was thwarted when he was arrested on 24 February by Iranian security agents in plain clothes, who reportedly failed to show him an arrest warrant.
According to a group of United Nations experts who examined his case, Vandecasteele was subjected to "multiple interrogations" and denied access to a lawyer.
Vandecasteele was initially held at the Evin prison and then moved blindfolded to a windowless room in an unknown location, the experts said.
He was later sentenced to a total of 40 years in prison in Tehran and a physical punishment consisting of 74 lashes.
The four charges related to alleged espionage against Iran, cooperation with the United States, currency smuggling and money laundering – accusations described as "arbitrary" and a "flagrant violation of international law" by the UN experts.
"We believe Mr Vandecasteele has been arbitrarily deprived of his liberty and is a victim of enforced disappearance for periods of detention," the experts said in a report released in January.
The UN panel received reports that indicated a weight loss of 15 kilos, "serious" health problems and a two-week hunger strike.
His deteriorating health triggered protests in solidarity across Belgium and piled further pressure on the central government to achieve a diplomatic solution that could bring the NGO worker back to his home country.
Relations between the West and Iran have taken a turn for the worse in recent months following the death of Mahsa Amini and growing evidence of Teheran's military assistance to Moscow amid Russia's invasion of Ukraine.