France summoned a senior Iranian diplomat on Thursday after two of its citizens were detained in Tehran in what Paris said was a baseless arrest, an incident likely to complicate ties between the countries as wider talks on reviving a nuclear deal stall.

Iran's intelligence ministry had said on Wednesday it had arrested two Europeans for allegedly fomenting "insecurity" there, but it had not revealed their nationalities.

"The French government condemns this baseless arrest. It calls for the immediate release of these two French nationals," the foreign ministry said in a statement, adding that Iran's Charge d'Affaires had been summoned.

The arrests come a week after a Swedish national was also detained and at a sensitive time, as the United States and parties to Iran's 2015 nuclear deal struggle to restore the pact that was abandoned in 2018 by then-U.S. President Donald Trump.

The EU's coordinator for the talks Enrique Mora has been in Tehran this week in what appeared to be another last ditch effort to salvage the accord.

"What I can see is an absence of progress on the nuclear file and in parallel provocations like these," a French diplomatic source told reporters ahead of a G7 foreign ministers meeting in northern Germany.

The two arrested were accused of "organising chaos and social disorder aimed at destabilising (Iran)" in conjunction with foreign intelligence services, Iranian state TV on Wednesday cited Iran's intelligence ministry as saying.

Christophe Lalande, federal secretary of France's FNEC FP-FO education union, told Reuters earlier on Thursday he suspected that one of his staffers and her husband, missing on a holiday in Iran, were the two arrested.

While there was no "absolute certainty", there was a "strong presumption" that it was her, Lalande said of his colleague, whom he named as Cecile Kohler. She was the union's international representative, he said.

Kohler had been due back in France earlier this week, he said, adding: "We have had no news from our friend."

French authorities did not confirm the name but a second diplomatic source said it was accurate.

Two other French nationals are held in Iran on national security charges their lawyers say are politically motivated.

Rights groups have accused Iran of trying to extract concessions from other countries through such arrests. Iran has repeatedly dismissed the charge.

Western powers have long demanded that Tehran free their citizens, who they say are political prisoners.

In January, an Iranian court sentenced French national Benjamin Briere to eight years in prison on spying charges, his Paris-based lawyer said, describing the trial as a politically motivated sham and his client as a "bargaining chip".

That same month, Iran re-imprisoned Franco-Iranian academic Fariba Adelkhah, sentenced to five years in jail in 2020 but recently living under house arrest.