Iranian state TV reports that 24-year-old Jamali Fashi has been hanged for the killing of a nuclear scientist in 2010.
Fashi was convicted in August of being an Israeli spy and of killing Tehran University physics professor Masoud Ali Mohammadi.
Mohammadi was killed in January 2010 when a motorcycle packed with explosives detonated outside his house as he was leaving for work.
Iran accuses Israel and the United States of killing at least four of its nuclear scientists and experts since 2010.
Based on reporting by AP and AFP