WASHINGTON－The United States and Iran completed a prisoner swap on Saturday, freeing one scholar from each country.

Released in Switzerland were Xiyue Wang, a US scholar who had been in Iranian custody since August 2016, and Iranian biomedical scientist Massoud Soleimani, held by the US for more than one year.

"After more than three years of being held prisoner in Iran, Xiyue Wang is returning to the United States," the White House issued a statement on Saturday on behalf of US President Donald Trump.

The US State Department tweeted a photo of Wang with the department's special envoy for Iran, Brian Hook, at the Zurich airport. Media reports said Wang flew to Switzerland from Iran and was met by Hook in Zurich.

Wang will reportedly undergo medical examination in Germany before returning to the US. "Thank you to Iran on a very fair negotiation," tweeted Trump.

"It was a one-on-one hostage swap," Trump said. "I think it was great to show that we can do something. It might have been a precursor as to what can be done."

Iranian Foreign Minister Mohammad Javad Zarif tweeted in welcome of the swap, saying both Wang and Soleimani "will be joining their families soon".

The Swiss Foreign Ministry confirmed that the exchange－which it called a "humanitarian gesture"－took place on its territory.

Wang, a graduate history student at Princeton University, was sentenced in 2017 to ten years in prison after being found guilty of being "an infiltrating American agent".Soleimani, a biomedical researcher with Teheran's Tarbiat Modares University, was arrested on arrival in Chicago from Iran last year and was charged with violating US trade sanctions against Iran.

The US and Iran have not had diplomatic ties since 1980, and relations have sharply worsened since Trump withdrew from an international accord giving Iran sanctions relief in return for curbs on its nuclear program.

The two countries came to the brink of military confrontation in June when Iran downed a US drone and Trump ordered strikes before canceling them at the last minute.

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