"Freeing Cecile Kohler and Jacques Paris is an absolute priority for us," Foreign Minister Jean-Noel Barrot said.

"We have always told our interlocutors from the Iranian regime that any decisions on sanctions will be conditional on resolving this issue."

Iran officially suspended its cooperation with the United Nations nuclear watchdog on Wednesday.

The move came after a 12-day conflict last month between Iran and Israel, which saw unprecedented Israeli and US strikes on Iran's nuclear facilities and sharply escalated tensions between Tehran and the International Atomic Energy Agency.

The United States and other Western countries, along with Israel, accuse Iran of seeking a nuclear weapon.

Tehran denies that, but has gradually broken away from its commitments under a 2015 nuclear deal it struck with world powers, after the United States pulled out of it in 2018.

Israel has maintained ambiguity about its own atomic arsenal, neither officially confirming nor denying it exists, but the Stockholm International Peace Research Institute estimates its arsenal amounts to 90 nuclear warheads.

The landmark 2015 Iran nuclear deal provided Tehran with sanctions relief in exchange for curbs on its atomic programme to be monitored by the UN nuclear watchdog.

The deal included the possibility of UN sanctions being reimposed through a mechanism called "snapback" if Iran failed to fulfil its commitments, an option that expires in October.

Israeli Foreign Minister Gideon Saar has urged European signatories of the 2015 deal to trigger the "snapback" mechanism and reinstate all UN sanctions on Iran.

Kohler, 40, and Paris, her 72-year-old partner, have been held in Iran since May 2022 on espionage charges their families reject.

But Iran has now charged the pair with spying for Israel's intelligence agency Mossad, diplomatic and family sources told AFP on Wednesday.

They were also accused of "corruption of Earth" and "plotting to overthrow the regime", the sources said. All three charges carry the death penalty.

Tehran has not confirmed the new charges.

A French diplomatic source described the allegations as "completely unfounded".

Iran is believed to hold around 20 European nationals, many of whose cases have never been publicised, in what some Western governments including France describe as a strategy of hostage-taking aimed at extracting concessions from the West.

Three other Europeans, who have not been identified, have also been arrested in the wake of the current conflict, two of whom are accused of spying for Israel, according to the authorities.