Ruling comes at time of rising tensions since President Donald Trump's arrival in White House in January
The Iranian judiciary on Sunday upheld 10-year jail terms for an American, two US-Iranian dual nationals and a Lebanese permanent resident of the United States for "collaborating" with Washington.
In a ruling that comes at a time of rising tensions since President Donald Trump's arrival in the White House in January, the Tehran prosecutor's office said the four men's appeals had been rejected.
Xiyue Wang, a Chinese-born American, was sentenced to 10 years in jail for "collaborating with foreign governments," said Tehran prosecutor Abbas Jafari Dolatabadi, quoted by the mizanonline website, which is close to the judiciary.
He said the same sentence was upheld against two dual nationals for "collaborating with a foreign government," and Lebanese national Nizar Zakka, a US permanent resident, for working with the American government.
The dual nationals, businessman Siamak Namazi and his father Mohammad Bagher Namazi, were convicted in October 2016 along with Zakka and three others on charges of "spying" for Washington.
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In Washington, Jared Genser, a lawyer for the Namazis, said in a statement carried by US media last week that their family was informed that a Tehran court had upheld the convictions days earlier.
Earlier in August, Princeton University and the wife of Wang, a history doctoral student and US citizen, said they had been informed that Iranian authorities had denied the appeal.
Wang was conducting dissertation research in Iran in 2016 when he was detained and charged with “spying under the cover of research,” an accusation his family and university denied.
Iran sentenced Zakka, a Lebanese citizen with permanent US residency, to 10 years in prison and a $4.2m fine in 2016 after he was found guilty of collaborating against the state, according to his US-based lawyer.
Zakka, an information technology expert, had been invited to Iran by a government official a year earlier, then disappeared after attending a conference in Tehran.
The State Department in July called on Iran to immediately release US citizens and other foreigners detained on "fabricated" national security charges, as Iran announced that Wang had been handed a 10-year sentence for "infiltration" and espionage.
"We call for the immediate release of all US citizens unjustly detained in Iran so they can return to their families," a State Department official said.
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"The Iranian regime continues to detain US citizens and other foreigners on fabricated national security-related charges," the official said.
"The safety and security of US citizens remains a top priority. All US citizens, especially dual nationals considering travel to Iran, should carefully read our latest travel warning."
Trump warned of "new and serious consequences" unless US nationals held in the Islamic republic were released, triggering criticism from Tehran of the detention of Iranian citizens in the US.
Iran's Foreign Minister Mohammad Javad Zarif accused Washington of holding Iranians on "charges of sanction violations that are not applicable today... for bogus and purely political reasons".
The State Department, for its part, says Iran continues "to harass, arrest, and detain US citizens, in particular dual nationals," warning that Washington's ability to assist is "extremely limited".
Severed ties, tensions
Ties between Washington and Tehran have been severed since April 1980 in the wake of Iran's Islamic revolution, and tensions have sharpened since Trump came to power in January, especially over Iranian missile tests.
Iran’s 2015 nuclear deal with world powers lifted most international sanctions and promised Iran’s reintegration into the global community in exchange for curbs on its nuclear programme.
The potential detente with the West has alarmed Iranian hardliners, who have seen a flood of European trade and investment delegations arrive in Tehran to discuss possible deals, according to Iran experts.
Security officials have arrested dozens of artists, journalists and businessmen, including Iranians holding joint American, European or Canadian citizenship, as part of a crackdown on “Western infiltration”.
The arrests have undermined President Hassan Rouhani’s goals of reviving business and political ties with the West, as well as pushing for more political and social reforms at home, Iran experts and observers said.
Although the US has imposed new unilateral sanctions over Iran's missile programme, Washington has so far honoured the nuclear accord despite Trump's threats as a candidate last year to "rip it up".