France says it has frozen the assets of Iran's Ministry of Security and Intelligence, as well as of two Iranian men thought to be members of the country's intelligence service, in a sign of deteriorating relations between the two countries.

The French government made the announcement in its official gazette on October 2, identifying one of the men as Assadollah Assadi, the same name as an Iranian diplomat who has been arrested over an alleged plot to bomb an Iranian opposition group in France in June.

The asset freeze also applied to Saeid Hashemi Moghadam, said to be the deputy minister and director-general of intelligence, and to the internal security directorate of the Intelligence Ministry.

"An attempted attack in Villepinte was foiled on June 30. An incident of such gravity on our national territory could not go unpunished," said a joint statement by the Foreign, Interior, and Economy ministries.

Worsening relations between Paris and Tehran come as the Iranians are trying to maintain ties with Europe after the United States pulled out of a nuclear accord that curtailed Iran's nuclear ambitions in exchange for lifting economic sanctions. France has been one of the staunchest advocates of salvaging the 2015 deal.

A German court said on October 1 it had approved Assadi's extradition to Belgium, where he is accused of masterminding the plot. Assadi was accredited as a counsellor at the Iranian Embassy in Vienna before his July detention in Germany.

Iran has denied the existence of any such plot, with Deputy Foreign Minister Abbas Araqchi saying the allegations were "aimed at damaging EU-Iran relations."

"We deny the accusations and forcefully condemn the Iranian diplomat's arrest and call for his immediate release," the Iranian Foreign Ministry said in an October 2 statement.

France gave no details of which assets are involved in the freeze, describing its measures as "targeted and proportionate."

It added that the government had acted against the "instigators, authors, and accomplices" of the foiled attack.

"Behind all this was a long, meticulous, and detailed investigation by our [intelligence] services that enabled us to reach the conclusion, without any doubt, that responsibility fell on the Intelligence Ministry," the Reuters news agency quoted an unidentified French diplomatic source as saying.

The source added that Moghadam had ordered the attack.

On June 30, Iranian opposition supporters gathered in Villepinte for a rally of the National Council of Resistance of Iran (NCRI), a Paris-based umbrella bloc of opposition groups that back the overthrow of Iran's clerical leadership.

That day in Brussels, law enforcement authorities apprehended two Belgian nationals of Iranian origin -- a husband and wife -- with 500 grams of explosive and a detonation device found in their car.

Meanwhile, French police detained an alleged accomplice of the pair in Paris. He was also described as a Belgian national of Iranian descent.

Assadi was taken into custody in Bavaria on July 1 on a European arrest warrant.

German prosecutors allege that he is an intelligence agent who met in late June with the husband-and-wife team in Luxembourg, where he handed the couple the explosives.

With reporting by Reuters and AFP