Story highlights Shahram Amiri had been in custody sicne returning to Iran in 2010

Amiri claimed CIA operatives had abducted him

U.S. officials said he provided "useful information"

(CNN) An Iranian nuclear scientist who once claimed he was kidnapped by the CIA has been executed after being accused of spying for the United States.

Shahram Amiri had been in custody in Iran since 2010.

"Shahram Amiri had access to the system's top secrets and had gotten connected with our number one enemy the Great Satan," Iranian judicial spokesman Hojjat al-Eslam Mehdi Mohseni-Ejehei told reporters Sunday, according to state news agency IRNA.

Amiri's case had been reviewed by the Iranian high court, which upheld the conviction, according to Mohseni-Ejehei. "The Iranian High Court reviewed this decision with extreme care given the allegations of espionage," he said.

The charge of treason in Iran could result in anything between 10 years in prison and the death penalty, Mohseni-Ejehei explained. But since the beginning of Amiri's case, all lower courts have ruled to execute, he added, according to IRNA.

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