Shahram Amiri's mother said the body of her son had been returned to their hometown with rope marks around his neck, showing that he had been hanged.  He was later buried. Amiri had been held at a secret location after returning from the US.

Some reports say he had in-depth knowledge of Iran's nuclear programme.  Amiri, who was born in 1977, went missing after taking a pilgrimage to Mecca in 2009.  He surfaced in the US a year later.

In a video he claimed he had escaped from US custody. He returned to Tehran in 2010 to a hero's welcome.  US officials said at the time that Amiri had defected of his own free will and provided 'useful information' to the US.

He was later reported to have been given a long prison sentence after his return to Tehran. 

His family confirmed at the time that he had been detained and told the BBC that they feared for his life.