An Iranian court has sentenced a French man to eight years in prison on spying charges, his family and Paris-based lawyer said Tuesday, arguing that Tehran was using him as a "hostage" in talks with the West.

Benjamin Briere, 36, is the only Western detainee known to be currently held in Iran who does not also hold an Iranian passport.

He was also given an additional eight-month sentence for propaganda against Iran's Islamic system, his lawyer Philippe Valent said in a statement.

Briere, who is being held in Vakilabad jail in the eastern city of Mashhad, was arrested in May 2020 after taking pictures in a national park with a recreational drone and is currently on hunger strike.

"This verdict is the result of a purely political process and... devoid of any basis," Valent said.

Calling the trial, which began Thursday, a "masquerade", he added that Briere "did not have a fair trial in front of impartial judges" and noted he had not been allowed to access the full indictment against him.

The French foreign ministry described the verdict as "unacceptable", saying Briere was a "tourist".

He is one of more than a dozen Western citizens held in Iran and described as hostages by activists who say they are innocent of any crime and detained at the behest of the powerful Revolutionary Guards to extract concessions from the West.

The verdict against Briere comes as Iran and world powers are seeking to reach agreement at talks in Vienna on reviving the 2015 deal over the Iranian nuclear programme.

Nationals of all three European powers involved in the talks on the Iranian nuclear programme -- Britain, France and Germany -- are among the foreigners being held.

"It is not tolerable that Benjamin Briere is being held a hostage to negotiations by a regime which keeps a French citizen arbitrarily detained merely to use him as currency in an exchange," Valent added.

Benjamin Briere is the only Western detainee known to be currently held in Iran who does not also hold an Iranian passport
Benjamin Briere is the only Western detainee known to be currently held in Iran who does not also hold an Iranian passport Saeid Dehghan's Twitter account via AFP

Briere's sister Blandine told AFP her brother is a "political hostage" subjected to a "parody of justice".

"It is a political trial and it is useful to Iran, which is sending a message to the French government," she said.

Valent said Briere was "more and more weakened" by a hunger strike he began at Christmas to protest the lack of progress in his case.

Briton Anoosheh Ashoori, held in Iran for the last four-and-a-half years, at the weekend also started a hunger strike, while Austrian Kamran Ghaderi, held for over six years, started refusing food on Monday, according to their families.

Their action was prompted by a hunger strike begun in Vienna by Barry Rosen, a former US diplomat and veteran of the 444-day hostage siege of the US embassy in Tehran from 1979-1981, to draw attention to the plight of the detainees.

He ended his hunger strike on Sunday to avoid further damage to his health.

Iran is also holding the French-Iranian academic Fariba Adelkhah, who was detained in June 2019 and sentenced to five years in prison in May 2020 on national security charges.

In October 2020, she was moved to house arrest but in a surprise development this month Iran jailed her again, saying she had violated house arrest rules.

Adelkhah was arrested with her French colleague and partner Roland Marchal, who was freed in March 2020 in an apparent prisoner swap after France released Iranian engineer Jallal Rohollahnejad.

Iran insists all the foreigners held are tried in line with domestic law but has repeatedly expressed readiness to prisoner swaps.