"Shahram Amiri was hanged for revealing the country's top secrets to the enemy (US)," Gholamhossein Mohseni Ejeie was quoted as saying by the Mizan Online news site.
Amiri disappeared in Saudi Arabia in June 2009 and resurfaced a year later in the United States. Iranian officials welcomed him on his return to Iran but there has been little information released since.
Amiri said after returning to the Islamic republic that he had been held in the US for more than a year after being "kidnapped" at gunpoint by two Farsi-speaking CIA agents in the Saudi city of Medina.
"America was outsmarted, since he couldn't imagine that (Iranian) intelligence services knew what he was doing and how he was taken to Saudi Arabia," Ejeie said.
Tehran and Washington have had no diplomatic ties since 1980, when students stormed the American embassy following the 1979 Islamic revolution.
Iranian nuclear scientist Shahram Amiri (L) standing with his father upon his arrival at Imam Khomeini Airport in Tehran, on July 15, 2010. AFP
Iran has executed a nuclear scientist convicted of handing over "top secret" information to the United States, a judicial spokesman said on Sunday.
