The Iranian judiciary on Sunday upheld 10-year jail terms for an American, two U.S.-Iranian dual nationals and a Lebanese permanent resident of the United States for “collaborating” with Washington, AFP reports.

The Tehran prosecutor’s office said the four men’s appeals had been rejected, according to the news agency.

Xiyue Wang, a Chinese-born American, was sentenced to 10 years in jail for “collaborating with foreign governments”, said Tehran prosecutor Abbas Jafari Dolatabadi. He was arrested while doing research in Iran for a university dissertation.

Three others facing similar charges have also had their jail sentences upheld. Two have joint US-Iranian citizenship, and one is Lebanese.

The US State Department accused Iran of “harassing, arresting and detaining US citizens”.

President Donald Trump recently warned of “new and serious consequences” unless U.S. nationals held in the Islamic Republic were released, triggering criticism from Tehran of the detention of Iranian citizens in the United States.

Iran’s Foreign Minister Mohammad Javad Zarif has accused Washington of holding Iranians on “charges of sanction violations that are not applicable today… for bogus and purely political reasons”.

In January 2016, the two countries conducted a groundbreaking prisoner swap by which Iranians held or charged in the US – mainly for breaching sanctions regulations – were released in exchange for Americans jailed in Iran.

Iran’s move comes amid continued tensions between Washington and Tehran. Iran signed a nuclear agreement with the U.S. five other world powers in 2015, but Trump has been a vocal critic of the Iran nuclear deal, which was signed during the term of the Obama administration. Trump has described the agreement it as “the worst deal I’ve ever seen negotiated” and threatened to annul it.