The agreement is set to be a first of its kind among European countries.
Belgian lawmakers have given their initial support to a controversial prisoner exchange treaty with Iran.
The agreement -- signed by Brussels and Tehran in March -- would allow the two countries to transfer convicted criminals to each other.
It was approved by a Belgian parliamentary committee on Wednesday, with the support of the majority and it will now be submitted to parliament.
Exiled Iranian opponents have slammed the treaty, arguing that it opens the door to "hostage diplomacy".
Critics also say the agreement could pave the way for a possible pardon of convicted terrorist Assadollah Assadi.
The 50-year-old Iranian diplomat was sentenced to 20 years in prison in February 2021 for "attempted terrorist assassination".
The court in Antwerp found him guilty of planning to commit a bomb attack at a gathering of Iranian opponents near Paris in June 2018.
Members of the targeted group have slammed the new treaty as "shameful".
During a debate in parliament on Tuesday, several MPs also accused the government of "a lack of transparency" around the treaty and of being pressurised by Iran.
Justice Minister Vincent Van Quickenborne has defended the deal, stressing the importance of freeing innocent people from the "authoritarian" Iranian regime.
"Our government has a moral duty to concern itself with the fate of innocent Belgian hostages, that is my priority at the moment," Van Quickenborne said on Wednesday.
At the start of the debate, the minister had revealed that Belgian aid worker, Olivier Vandecasteele, had been held "arbitrarily" in Tehran since 24 February.
The 41-year-old had been carrying out humanitarian work in Iran since 2015 and has been “illegally” held on espionage charges for four months, according to Brussels.
The Belgian-Iranian treaty may also help release Swedish-Iranian academic Ahmadreza Djalali, who has taught in Belgium and has been sentenced to death in Iran.
"People's lives are at stake," Van Quickenborne said on Tuesday.
"If the bill is not fully approved, the threat to our Belgian interests and certain Belgian citizens will increase."