TEHRAN, Iran >> Iran executed a nuclear scientist who defected to the U.S. and returned to the Islamic Republic under mysterious circumstances a year later, an official said Sunday, acknowledging for the first time that the nation secretly detained, tried and convicted a man authorities once heralded as a hero.

Shahram Amiri vanished in 2009 while on a religious pilgrimage to Muslim holy sites in Saudi Arabia, only to reappear a year later in a series of contradictory online videos filmed in the U.S. He then walked into the Iranian interests section at the Pakistani Embassy in Washington and demanded to be sent home.

In interviews, Amiri described being kidnapped and held against his will by Saudi and American spies, while U.S. officials said he was to receive millions of dollars for his help in understanding Iran’s contested nuclear program. He was hanged the same week as Tehran executed a group of militants, a year after his country agreed to a landmark accord to limit uranium enrichment in exchange for the lifting of economic sanctions.

Speaking to journalists Sunday, Iranian judiciary spokesman Gholamhosein Mohseni Ejehi said Amiri was convicted of spying charges in a death-sentence case upheld by an appeals court.

“This person who had access to the country’s secret and classified information had been linked to our hostile and No. 1 enemy, America, the Great Satanm” Ejehi said. “He provided the enemy with vital and secret information of the country.”

Ejehi did not explain why authorities never announced Amiri’s conviction, though he said Amiri had access to lawyers.

News about Amiri, born in 1977, has been scant since his return to Iran. Last year, his father Asgar Amiri told the BBC’s Farsi-language service that his son had been held at a secret site. Ejehi said Amiri’s family mistakenly believed he only received a 10-year prison sentence.

On Tuesday, Iran announced it had executed a number of criminals, describing them mainly as militants from the country’s Kurdish minority. Then, an obituary notice for Amiri circulated in his hometown of Kermanshah, a city some 500 kilometers (310 miles) southwest of Tehran, according to the Iranian pro-reform daily newspaper Shargh.

Manoto, a private satellite television channel based in London believed to be run by those who back Iran’s ousted shah, first reported Saturday that Amiri had been executed. BBC Farsi also quoted Amiri’s mother saying her son’s neck bore ligature marks suggesting he had been hanged by the state.

The Associated Press could not immediately reach Amiri’s family.

Amiri’s disappearance came amid a concerted Western effort to thwart Iran’s nuclear program under the government of hard-line President Mahmoud Ahmadinejad. The Stuxnet computer virus, widely believed to be a joint U.S.-Israeli creation, had begun disrupting thousands of centrifuges at a uranium enrichment facility in Iran. The U.S. also actively recruited nuclear scientists to defect, while a series of bombings suspected to be carried out but never acknowledged by Israel killed others.

In June 2010, a shaky online video emerged of Amiri saying he had been kidnapped by American and Saudi agents and was in Tucson, Arizona.

A short time later, he appeared in a professionally shot online video near a chess set, saying he wanted to earn a doctorate in America and return to Iran if an “opportunity of safe travel” presented itself. His wife and son remained behind in Iran.

“I have not done any activity against my homeland,” he said. But soon, another clip by him contradicted that and then he appeared at the Pakistani Embassy.

Hillary Clinton, then-U.S. secretary of state, stressed Amiri had been in America “of his own free will.”

“He is free to go,” she said.

U.S. officials at the time told the AP that Amiri was paid $5 million to offer the CIA information about Iran’s nuclear program, though he left the country without the money. They said Amiri, who ran a radiation detection program in Iran, travelled to the U.S. and stayed there for months under his own free will. Analysts abroad suggested Iranian authorities may have threatened Amiri’s family back in Iran, forcing him to return.

But when he returned to Iran and was welcomed with flowers by government officials, Amiri said Saudi and American officials had kidnapped him while he visited the Saudi holy city of Medina. He also said Israeli agents were present at his interrogations and that that CIA officers offered him $50 million to remain in America.

“I was under the harshest mental and physical torture,” he said.

Amiri’s case indirectly found its way back into the spotlight in the U.S. last year with the release of State Department emails sent and received by Clinton, now the Democratic presidential candidate. The release of those emails came amid criticism of Clinton’s use of a private account and server that has persisted into her campaign against Republican candidate Donald Trump.

An email forwarded to Clinton by senior adviser Jake Sullivan on July 5, 2010 — just nine days before Amiri returned to Tehran — appears to reference the scientist.

“We have a diplomatic, ‘psychological’ issue, not a legal one. Our friend has to be given a way out,” the email by Richard Morningstar, a former State Department special envoy for Eurasian energy, read. “Our person won’t be able to do anything anyway. If he has to leave so be it.”

Another email, sent by Sullivan on July 12, 2010, appears to obliquely refer to the scientist just hours before his appearance at the Pakistani Embassy became widely known.

“The gentleman … has apparently gone to his country’s interests section because he is unhappy with how much time it has taken to facilitate his departure,” Sullivan wrote. “This could lead to problematic news stories in the next 24 hours.”