Zurich was the scene of a rare prisoner swap between Iran and the United States on Saturday. Iranian foreign minister Javad Zarif and US official Brian Hook coordinated the swap of prisoners Massoud Soleimani and Xiyue Wang.

US citizen Xiyue Wang will be returning to the United States after being held prisoner in Iran for 3 years on spying charges.

Professor Soleimani is a scientist who was facing trial for allegedly trying to export biological material to Iran in breach of US sanctions.

Minister Zarif tweeted soon after the successful swap: "Glad that Professor Massoud Soleimani and Mr. Xiyue Wang will be joining their families shortly".

The rare swap also acted as a symbolic gesture of cooperation between the two longtime enemies whose relationship has worsened since American President Donald Trump took office.

Professor Soleimani was expected to return to Iran after the exchange.

Hook and Wang were travelling to Landstuhl in Germany, which is home to an American medical center in which Wang will be examined by doctors. He is expected to remain in Germany for several days before returning to the United States.