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, Reuters reported.
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 quoted by Reuters, adding that Iran's Charge d'Affaires had been summoned.
The two arrested were accused of "organizing chaos and social disorder aimed at destabilizing (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.
Iran regularly says it captured spies from enemy countries, such as the US and Israel, but sometimes it reports the arrests of other nationals.
In August of 2019, Iran jailed two people, including a British dual national, for 10 years for spying for Israel.
In June of that year, a former Iranian Department of Defense contractor was executed by Iran for spying for the US government.
In 2020, Iran sentenced eight environmental activists, including an Iranian who reportedly also has British and American citizenship, to prison sentences ranging from four to 10 years on charges of spying for the United States.
Earlier this week, Iran announced it intends to execute Swedish-Iranian doctor Ahmadreza Djalali, who was convicted of spying for Israel.
Djalali, a disaster medicine researcher, was arrested in 2016 during an academic visit to Iran and put on trial on suspicion of espionage for Israel's Mossad spy agency. He was convicted a year later and sentenced to death.