A Chinese-born US citizen sentenced to 10 years in prison in Iran on spying charges has been released as part of a prisoner swap. Princeton graduate student Xiyue Wang, imprisoned since 2016, was exchanged for Masoud Soleimani, an Iranian scientist arrested at Chicago airport last year and convicted on charges of violating US trade sanctions. Wang was due to fly to the US via Oman and a US military base in Frankfurt, Germany. There had been no prior indication he was due to be released, and he was apparently shocked when he was told the news. He initially travelled to Iran to study Farsi and Iranian history. In a statement, President Donald Trump said: “Mr. Wang had been held under the pretense of espionage since August 2016. We thank our Swiss partners for their assistance in negotiating Mr. Wang’s release with Iran.” The Swiss embassy in Tehran looks out for America’s interests in the country as the US embassy there has been closed since the 1979 student takeover and 444-day Iran hostage crisis.