Iranian-Swedish academic Ahmadreza Djalali, who is on death row in Iran’s Evin prison, has started a hunger strike to protest being left out of a recent Tehran-Stockholm prisoner exchange, his wife said.

Djalali's wife Vida Mehrannia told AFP on Tuesday that her husband believes "the only way anyone can hear his voice in the world is to just start a hunger strike."

Earlier in June, two Swedish nationals imprisoned in Tehran were exchanged with Hamid Noury, a former Iranian prison official sentenced to life in Sweden for his role in the 1988 mass killings in Iranian jails.

Last week, Djalali criticized Swedish Prime Minister Ulf Kristersson for excluding him from the prisoner exchange, expressing his despair from Evin prison: "You left me here, helpless. Why not me?"

Djalali was arrested in April 2016 on espionage accusations, while visiting Iran on an academic trip.

He was sentenced to death in October 2017 on the charge of "corruption on earth" in what Amnesty International described as a "grossly unfair trial."