The families of two Austrian-Iranians jailed in Iran criticised the government in Vienna for failing to publicly highlight their cases as the city hosts talks on the future of the 2015 nuclear deal.
The families of Massud Mossaheb, 74, and Kamran Ghaderi, 56, said Austria's silent diplomacy failed to bring them home despite each being sentenced to 10 years in prison on what supporters said were baseless espionage convictions.
Mr Ghaderi, a businessman, has been in prison for more than five years and concerns for his health were increasing.
Mr Mossaheb has been in prison since January 2019 and he was accused of spying for Israel's intelligence agency Mossad and Germany.
The families said the men were tortured and forced to confess.
Their cases were raised by the UN, but the families said that Austrian Foreign Minister Alexander Schallenberg has been silent.
"You do not publicly request their release, nor do you publicly acknowledge the injustice, torture and illegality of their imprisonment," the families said in an open letter to the minister.
“After years of continuing to rely on 'silent diplomacy’ we interpret this either as a sign of resignation, a lack of commitment or a lack of will to consider alternative strategies.”
The Austrian foreign ministry said the plight of dual citizens was at the "top of our agenda" and the issue raised during the talks in Vienna.
But Iran does not recognise dual nationality for Iranians which meant that consular protections for inmates were "very limited or sometimes even non-existent".
The families compared the strategy with a statement by Austria’s parliament that it would not allow basic values to be “trampled underfoot” by Russia over the case of the jailed opposition leader Alexei Navalny.
"Your silence concerning the fate of the two Austrians Mossaheb and Ghaderi stands in clear discrepancy," the families said.
The men are among at least 16 EU and US dual citizens held in Iran.
Mr Ghaderi, the chief executive of an IT firm and father of three, was arrested after he arrived in Tehran on a business trip.
While in prison, he has had operations on his back and scans for a tumour on his leg.
He is held in a room with 15 other prisoners, his wife, Harika Ghaderi, said.
“Every time I ask the Austrian government about what they are planning, the answer is the same: they are trying their best at a high diplomatic level,” she said.
“My criticism is that he is still in prison after five years. I don’t know what’s being done now, but it shows that it has not been enough. We have missed him every minute of our lives.”
Austria hosted talks on the peace deal this week, bringing hope the US would return to the treaty after president Donald Trump abandoned it in 2018.
The Austrian foreign ministry said: "We have been consistently advocating for their unconditional release in all our contacts with the Iranian government at all levels. Austrian citizens imprisoned abroad are entitled to consular protection.
"We constantly work on obtaining improvements of prison conditions and adequate medical treatment for the persons concerned.
"In our efforts, we are in close touch with the families’ of the prisoners. Our ultimate goal is the prisoners’ release and to see them reunited with their families and loved ones."
A letter signed by 20 families of detainees and former inmates said this week that more dual citizens would be seized and wrongfully jailed in Iran if the US failed to link the fate of foreign hostages to restoring the pact.
All prisoners must be freed and Tehran must commit to stop taking hostages as a condition of resuming the nuclear deal, they said.
Iran welcomed signs that President Joe Biden's administration was to lift sanctions imposed by Mr Trump in 2018. In contrast to the US, Austria joined European allies in seeking avenues to continue trade with Iran in support of the nuclear deal.