A Belgian court jailed an Iranian diplomat for 20 years on Thursday after convicting him of plotting the thwarted 2018 bombing of an opposition rally outside Paris.
The trial was conducted under tight security in the Belgian port of Antwerp and has further poisoned already tense relations between Tehran and European capitals.
The terrorism conviction was also claimed as a victory by cheering onlookers from the exiled National Council of Resistance in Iran (NCRI), the opposition group that was targeted for attack.
Assadollah Assadi, now 49, was attached to the Iranian mission in Austria when he supplied explosives for an attack that was planned for a June 30, 2018 NCRI rally in France.
Belgian officers foiled the attack when they intercepted a car carrying the device, and Assadi was arrested the next day in Germany, where he was deemed unable to claim diplomatic immunity.
Three of his accomplices, dual Iranian-Belgians, were also arrested and on Thursday were given jail terms of between 15 and 18 years and stripped of their Belgian citizenship.
The 2018 gathering in Villepinte, near Paris, included senior NCRI leaders and some high-profile supporters, including former US president Donald Trump's personal lawyer Rudy Giuliani.
The case has shone a light on Tehran's international operations just as it hopes the arrival of new US President Joe Biden will herald a loosening of sanctions re-imposed by Trump.
Iranian foreign ministry spokesman Saeed Khatibzadeh said "the Islamic Republic of Iran strongly condemns" the sentences, and dubbed the trial "illegal and in flagrant violation of international law".
Assadi's defence counsel Dimitri de Beco told AFP that his client would "probably" appeal the verdict, but that he would give him time to decide.
There have been concerns Iran may react to the case by detaining European nationals or increasing pressure on detainees like Iranian-Swedish academic Ahmadreza Djalali, a guest lecturer at Belgium's VUB university.
Djalali has been sentenced to death for espionage and Belgium's justice minister Vincent Van Quickenborne told AFP: "We are obviously worried about his fate and continue to demand of the Iranian authorities that they not apply the death penalty."
But he stressed that the Belgian court's verdict and the rule of law must be respected. "If a judge needs to take international relations into account, then we're no longer talking about an independent judgment."
Dressed as a tourist
Assadi was charged with "attempted murders of a terrorist nature" and "taking part in the activity of a terrorist group".
Iran had warned even before the conviction that it would not recognise the trial or the verdict, denying any official role in the plot and insisting Assadi ought to have enjoyed immunity from prosecution.
But investigators concluded that he was an Iranian agent working under diplomatic cover.
They showed the court surveillance pictures of Assadi dressed as a tourist, in a hat and with a camera, handing the Belgian-Iranian couple a package in Luxembourg on June 28, 2018.
The couple - Nasimeh Naami, 36, and Amir Saadouni, 40 - were found to have accepted from Assadi a half-kilo of TATP explosives and a detonator.
Naami, painted in court as highly manipulative, received an 18-year sentence and Saadouni 15 years.
Belgium-based Iranian former dissident Mehrdad Arefani was found to have been an accomplice of Assadi's who had been due to guide the couple at the rally.
He was the only defendant to agree to appear in court for the sentencing and sat impassively as he was jailed for 17 years.
Belgian officers halted the couple's car with the bomb on board on the day of the event, preventing what the NCRI's lawyers said would have been a "bloodbath".
Later that year, the French government accused Iran's intelligence service of being behind the operation, a charge the Islamic Republic has furiously denied.
Iran's regime 'on trial'
The case stirred tensions between European powers and Tehran, and was seized upon by NCRI supporters to press their case against the Iranian regime.
The group's leader Maryam Rajavi tweeted that the convictions dealt "a heavy political and diplomatic blow to the regime in Iran".
Toby Dershowitz, of Washington think-tank the Foundation for Defence of Democracies said: "This case is not an aberration but rather is part of a pattern of the Islamic Republic's terrorism in Europe and around the world."
Dershowitz urged European governments to suspend diplomatic ties with Iran as some did briefly in 1997 after a German court implicated Iran in the 1992 murders of four opposition exiles.
A European Commission spokesman said Brussels would consider the verdict, and that Assadi's name had been added to its terrorist blacklist.