Amiri's family announced they received his body last Wednesday and buried him in his hometown of Kermanshah. His mother says there were signs of rope on her sons neck which apparently showed he was hanged, she said.
No official statement has so far been made about the scientist's death who had previously been sentenced to 10 years of imprisonment after authorities charged him for revealing "sensitive information" about Iran's nuclear reactors.
Amiri went missing in Saudi Arabia in 2009 after a pilgrimage to the country. He surfaced in the US a year later and said he was taken by CIA agents to the US under force.
US officials said at the time that the young scientist had travelled to the country voluntarily and provided them with "valuable information" about Iran's nuclear activities.
He returned to Iran later in 2010 to a hero's welcome with the state TV showing his arrival at the airport.
Amiri was born in 1978 in the Kurdish city of Kermanshah and was a graduate of the nuclear science faculty at Malek Ashtar University of Technology in Tehran.
His death follows the execution of another 20 Kurdish Sunni activists in Iran who were hanged last Tuesday in Iran's Rajayi prison in Tehran.
