However, since he was arrested in Germany and his diplomatic accreditation was in Austria, Belgian prosecutors say they have the right to prosecute.
Formerly based in Vienna, Assadi faces a 20-year prison sentence if found guilty of the attack that was foiled in June 2018. Prosecutors have called for a full sentence without leniency.
The trial was to continue with lawyer Dimitri de Beco, representing his client.
Three others are on trial: a Belgian Iranian couple – Nasimeh Naami, 36, and Amir Saadouni, 40, accused of taking Assadi’s bomb and planting it at the opposition rally – and Mehrdad Arefani, 57 , an Iranian poet based in Belgium who has frequent telephone contact with the diplomat.
The three co-defendants appeared in court. Prosecutors have asked for an 18-year term for the couple and 15 years for Arefani.
All four are accused of attempting to carry out an armed attack and of participating in the activity of an armed group.
After Friday’s session, the second part of the trial is scheduled to take place on Thursday. The court should then adjourn to consider its verdict before ruling early next year.
The case throws an uncomfortable light on Tehran’s international activities as it hopes for a thaw in relations with the West as US President Donald Trump, who has pulled Washington out of the Iran nuclear deal, is due to step down.
In June 2018, Belgian authorities thwarted what they said was an attempt to smuggle explosives into France to attack a meeting of one of Iran’s exiled opposition movements attended by close allies of Iran. Trump.
Later in the year, the French government accused Iranian intelligence of being behind the operation, an accusation that the Islamic Republic furiously denied.
The National Council of Resistance in Iran (NCRI), which includes the People’s Mojahedin of Iran (MEK), held its rally in Villepinte, near Paris, on June 30, 2018.
Several well-known international figures, including Trump’s lawyer Rudy Giuliani and former British officials, as well as former Franco-Colombian senator Ingrid Betancourt and NCRI leader Maryam Rajavi, were to attend.
On the day of the rally, Belgian police intercepted Naami and Saadouni from Antwerp with half a kilogram (about 1.1 pounds) of TATP explosives and a detonator in their car.
Assadi was arrested while traveling through Germany where he had no immunity from prosecution.
Arefani, who had lived in Belgium for more than 10 years, was arrested in France in 2018 after Belgium issued a European arrest warrant.
“We cannot imagine the scale of the avoided disaster,” declared lawyer Georges-Henri Beauthier, representing the NCRI, alongside his French colleague William Bourdon.
In court, Bourdon said: “This is an unprecedented historic trial. It is the first time that, symbolically, the mullahs’ regime is on the dock.
The lawyer representing those targeted by the alleged attack said Arfani was close to Assadi, who is believed to be the architect of the plot, and pointed to an Austrian SIM card found in his possession.
The two men deny any connection.
De Beco, Assadi’s lawyer, accused the civilian plaintiffs of trying to turn the case into a political trial on behalf of the opposition movement.
According to Iranian expert François Nicoullaud, former French ambassador to Tehran, Iranian President Hassan Rouhani was surprised to learn that the attack failed.
“Visiting Europe at the time, he was absolutely furious to learn of the existence of this intelligence service operation,” the diplomat told AFP news agency.
At the time of the alleged plot, Rouhani was trying to maintain support from European capitals for the 2015 Iran nuclear deal, which remains alive as European capitals attempt to keep Iran on board.