The Sunday report quotes an unnamed official as saying Vahid Sayyadi Nasiri died in a hospital a week after he was transferred there from a prison in Qom, some 120 kilometers south of the capital Tehran.
Earlier last week authorities confirmed Nasiri's death, without providing details.
Deputy Spokesman of the State Department Robert Palladino had on Thursday condemned Iran in a tweet for death of Nasiri saying he died "protesting arbitrary detention and inhumane prison conditions."
Iran has sentenced dozens of activists to varying prison terms over security charges.
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