The mother of Shahram Amiri said the body of her son was sent to their hometown with rope marks around his neck, leading to the conclusion that he was hanged. Gholam-Hossein Mohseni-Eje'i, a deputy Chief Justice of Iran, said Amiri "provided the enemy with vital information of the country". The scientist's execution was confirmed by Iran's official news agency, IRNA.
Amiri had been held at a secret location in Iran after returning from the US. He claimed he had been kidnapped by the CIA. The scientists said in a video recording, reportedly filmed in the US: "They took me to a house located somewhere that I didn't know. They gave me an anaesthetic injection."
In 2009, Amiri travelled to the US after making a Hajj pilgrimage to Mecca. He later said that he had been kidnapped and placed under "intense psychological pressure to reveal sensitive information" by the CIA, in a BBC report.
This was contradicted by US officials in 2010, who stated that they had paid Amiri a sum of $5m (£3.83m) to defect and provide "significant" information about Iran's atomic programme, according to an AP report. The New York Times reported that he had been a CIA spy working inside Iran for many years.
Some media outlets stated that he worked for Malek-Ashtar University of Technology, which is associated with Iran's Ministry of Defense. On the billboard announcing his death, he is referred to as "Dr Shahram Amiri".
Mystery surrounds the reasons why Amiri returned to Iran. In an interview with Saham News, his family said that they "had been taken hostage" a month before the scientist came back to Iran, an oblique reference that Iranian security forces had used his family to force his return.
He was arrested in 2012 and a military court sentenced him to a 10-year jail sentence for providing classified information to the "enemy", according to Iran Wire.
Amiri was buried in his hometown of Kermanshah, 310 miles south-west of Tehran.