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 following 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 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.

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 Xiyue, a Princeton University researcher, 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.

‎"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 United States.

"You are keeping our innocent citizens in gruesome prisons. This is against the law and international norms and regulations," said Sadegh Larijani, the head of Iran's judiciary.

"We tell them that you must immediately release Iranian citizens locked up in US prisons."

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".

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.

Tehran and world powers, including Washington, signed a July 2015 accord curbing Iran's nuclear programme in exchange for a lifting of sanctions.

Although it 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".

Source: AFP