Iran executed prisoner Afshin Rahimi-Hedayat on drug-related charges in Hamadan Central Prison in Hamadan Province on 10 August.
Rahimi-Hedayat and another death row prisoner were moved to solitary confinement in recent days for execution.
There is no information about the identity and the situation of the other prisoner.
Rahimi-Hedayat, 30, from Kangavar in Kermanshah Province, was arrested about four years ago and sentenced to death for drug-related offences.
In recent days, at least four civilians from Kangavar, Mohsen Yaghouti, Hamzeh Farrokhi, Manouchehr Khazaei and Afshin Rahimi-Hedayat were executed for drug-related charges in Hamadan Central Prison.