TEHRAN:  Iran executed a nuclear scientist convicted of spying for the United States, an official said Sunday, acknowledging for the first time that the nation secretly detained and tried a man who was once heralded as a hero.

Shahram Amiri defected to the US at the height of Western efforts to thwart Iran's nuclear program. When he returned in 2010, he was welcomed with flowers by government leaders and even went on the Iranian talk-show circuit. Then he mysteriously disappeared.

He was hanged the same week that Tehran executed a group of militants, a year after Iran agreed to a landmark accord to limit uranium enrichment in exchange for the lifting of economic sanctions.

Amiri first vanished in 2009 while on a religious pilgrimage to Muslim holy sites in Saudi Arabia. A year later, he reappeared in a series of contradictory online videos filmed in the US. He then walked into the Iranian-interests section at the Pakistani Embassy in Washington and demanded to be sent home.

In interviews, he described being kidnapped and held against his will by Saudi and American spies. US officials said he was to receive millions of dollars for his help in understanding Iran's nuclear program.

Iranian judiciary spokesman Gholamhosein Mohseni Ejehi said Amiri "had access to the country's secret and classified information" and "had been linked to our hostile and No. 1 enemy, America, the Great Satan."

The spokesman told journalists that Amiri had been tried in a death-penalty case that was upheld by an appeals court. He did not explain why authorities never announced the 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 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 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 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, 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.

His disappearance came as Western countries stepped up their efforts to impede Iran's nuclear program under the government of hard-line President Mahmoud Ahmadinejad. The US actively tried to recruit nuclear scientists to defect. Later, four Iranian nuclear scientists were assassinated between 2010 and 2012, and Iran blamed the slayings on Israel and the West.

The Stuxnet computer virus, widely believed to be a joint US-Israeli creation, also disrupted thousands of centrifuges at a uranium enrichment facility in Iran at the same time.

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 contradicted that, and he appeared at the Pakistani Embassy.

Hillary Clinton, who was then the secretary of state, stressed that Amiri had been in America "of his own free will."

"He is free to go," she said.

US 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, traveled to the US and stayed there for months by choice.

Analysts abroad suggested Iranian authorities may have threatened Amiri's family back in Iran, forcing him to return.

On his return from the US, Amiri was greeted at airport by high-ranking government officials and was invited to TV talk shows where he explained how he bypassed a US trap to get home. Many newspapers published accounts of his return on their front pages and some suggested a movie be made from his story.

He said Saudi and American officials had kidnapped him while he visited the Saudi holy city of Medina. He 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 US 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 10 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."