Assadi, who was arrested while on holiday in Germany and handed over to Belgium, is refusing to appear in court and did not attend the first day of the trial in Antwerp
An Iranian diplomat and three other Iranians went on trial in Belgium on Friday accused of planning to bomb a meeting of an exiled opposition group in France in 2018, the first time an EU country has put an Iranian official on trial for terrorism.
Belgian prosecutors charged Vienna-based diplomat Assadolah Assadi and the three others with plotting an attack on a rally of the Paris-based National Council of Resistance of Iran (NCRI). The rally's keynote address was given by US President Donald Trump's lawyer, Rudy Giuliani.
Assadi, who was arrested while on holiday in Germany and handed over to Belgium, is refusing to appear in court and did not attend the first day of the trial in Antwerp; he has not commented on the charges.
"My client asked me to represent him today, he let me know he has the fullest respect for these judges but as he considers that he should benefit from immunity, they are not allowed to judge him," his lawyer Dimitri de Beco told Reuters.
Assadi was the third counsellor at Iran's embassy in Vienna. French officials have said he was in charge of intelligence in southern Europe and was acting on orders from Tehran.
The Islamic Republic has repeatedly dismissed the charges, calling the attack allegations a "false flag" stunt by the NCRI, which it considers a terrorist group.
The trial is expected to continue next week, with a possible verdict later this month or in early January, lawyers said.
Assadi warned authorities in March of possible retaliation by unidentified groups if he is found guilty, according to a police document obtained by Reuters.
Authorities say the attack was thwarted by a coordinated operation between French, German and Belgian security services.
Two of Assadi's suspected accomplices were arrested in Belgium with the explosive TATP and a detonator. Their lawyers said on Friday that neither had any intention to kill.
Lawyers representing participants of the 2018 rally, who are a civil party to the Belgian prosecution, have argued that diplomatic immunity cannot be used as a cover to carry out a terrorist attack, which carries a maximum 20-year prison term.
"I think the words 'brave little Belgium' are entirely appropriate today," said Rik Vanreusel, a lawyer for the civil party. "We are one of the only countries that has dared to put such rather politically sensitive matters in a proper perspective."
Following a 2015 accord between Iran and world powers to curb Tehran's nuclear programme, the European Union has sought closer diplomatic and economic relations with Tehran, but says it cannot turn a blind eye to human rights abuses or terrorism.
France has said Iran's intelligence ministry was behind the 2018 plot and it expelled an Iranian diplomat.
European countries have blamed Iran for other suspected moves against dissidents, including two killings in the Netherlands in 2015 and 2017 and a foiled assassination in Denmark. The Islamic Republic has denied involvement.