President Trump pulled out of the nuclear accord this year, pronouncing the Iranian government a rogue actor and the 2015 deal as wholly insufficient to rein in its ambitions, as well as doing nothing to halt its meddling and support of regional conflicts. In contrast, European countries are trying to find a way to avoid pulling out of the deal because they think doing so will worsen Iran’s relationship with the West.

At the same time, the decision to freeze the assets of the spy ministry seemed to be a clear sign France was angry that Iran appeared to be ignoring international norms and acting with impunity. It also indicated that, at least indirectly, France endorsed Mr. Trump’s judgment that Iran was a rogue regime.

An Iranian foreign ministry spokesman, Bahram Qasemi, denied that Iran had been involved in a bombing plot, the state news agency IRNA reported.

The assets of two of the Iranians believed to have been behind the plot have also been frozen, the French ministers said. One is a former Iranian diplomat in Vienna, Assadollah Asadi; the background of the other, Saeid Hashemi Moghadam, was not specified. But French news media reported that he was a senior official at the Iranian Intelligence and Security Ministry.

There were several people detained at the time the plot was unveiled, with the Belgium police taking the lead by arresting two Belgian-Iranian citizens, a husband and wife, who were accused of preparing to drive to France to carry out the bombing.