Ahmadreza Djalali, formerly based in Stockholm where he worked at the Karolinska Institute, was arrested during a visit to Iran in April 2016.
He was sentenced to death in 2017 after being found guilty of passing information about two Iranian nuclear scientists to Israel’s Mossad spy agency that led to their assassinations.
Citing informed sources, ISNA news agency said on Wednesday that his death sentence would be carried out by May 21.
Djalali was granted Swedish citizenship while in detention in February 2018, a few months after Iran’s supreme court confirmed the death sentence.
United Nations rights experts said in March 2021 that he was in critical condition after months of solitary confinement and called for his release.
Wednesday’s report comes on the last day of the trial in Stockholm of Hamid Noury, a former Iranian prison official.
Noury, 61, stands accused of crimes against humanity and war crimes for alleged involvement in the executions of a large number of inmates in the 1980s.
The prosecution said the prisoners were members of the People’s Mujahedin of Iran, an exiled opposition organisation that Tehran considers a “terrorist group”, as well as other outlawed groups.
Lawyers for Noury, who was arrested at Stockholm airport in November 2019, have denied he was present for the alleged killings.
Iran said on Monday that it had summoned Sweden’s ambassador after prosecutors in the Nordic country sought a life sentence for Noury.