An Iranian diplomat has been jailed for 20 years over a failed bomb plot in France that has stoked tensions between the EU and Tehran even as they scramble to save a landmark international nuclear deal.

Assadolah Assadi was sentenced by a Belgium court on Thursday over the conspiracy to target a 2018 Iranian opposition rally addressed by Rudy Giuliani, lawyer to former US president Donald Trump.

The case was one of several involving Tehran’s alleged pursuit of Iranian dissidents in Europe that has complicated efforts by EU countries and Iran to save the nuclear accord that the US quit in 2018 under Mr Trump. His successor President Joe Biden has said Washington was prepared to rejoin the agreement as long as Iran abides by its commitments.

Assadi, an official with the Iranian embassy in Vienna, was arrested in Germany and transferred to and tried behind closed doors in Belgium. Authorities have alleged that he carried the explosives for the bombing on a flight from Iran to Austria, Belgian prosecutors said.

“The ruling shows two things: a diplomat doesn’t have immunity for criminal acts . . . and the responsibility of the Iranian state in what could have been carnage,” Georges-Henri Beauthier, a prosecution lawyer, said outside the court in Antwerp, according to Reuters.

Mr Giuliani gave the keynote speech at the rally held by the National Council of Resistance of Iran. Assadi and his lawyers have not commented on the case. Iran has dismissed the case as a fabrication.

The EU imposed sanctions in January 2019 on an alleged Iranian intelligence organisation and two of its agents over the plot and another alleged conspiracy to murder an opposition figure in Denmark. The Netherlands has also accused Tehran of two killings of Dutch nationals of Iranian origin in 2015 and 2017.

Officials from the Netherlands, Britain, France, Germany, Denmark and Belgium told Iranian counterparts of “their serious concerns regarding Iran’s probable involvement in these hostile acts on EU territory”, according to a letter published in January 2019 by the Dutch government.