Earlier in the day, judicial spokesman Gholam Hossein Mohseni-Ejei announced that a U.S. citizen had been sentenced for "infiltration" but did not give further details.
"It was verified and determined that he was gathering [information] and was involved in infiltration," Mohseni-Ejei said at a news conference in Tehran, the Associated Press reported.
Mizan, which is affiliated with Iran's hard-line judiciary, later reported that Wang was sentenced as part of an "infiltration project" that included the gathering of "confidential articles" to send to the State Department and Western academic institutions.
Wang is a fourth-year graduate student working on a doctorate in history, Daniel Day, Princeton's vice president of communications, said Sunday.
"He was arrested in Iran last summer, while there doing scholarly research on the administrative and cultural history of the late Qajar dynasty in connection with his Ph.D. dissertation," Day said in a statement. "Since his arrest, the university has worked with Mr. Wang's family, the U.S. government, private counsel and others to facilitate his release.
"We were very distressed by the charges brought against him in connection with his scholarly activities, and by his subsequent conviction and sentence."
Stephen Kotkin, Wang's adviser at Princeton, described him as a gifted scholar who was impressed with Persian culture.
"Xiyue Wang is a remarkable, linguistically gifted graduate student studying late 19th- and early 20th-century governance in predominantly Muslim regions — Qajar Iran, Afghanistan, imperial Russian Turkestan," he said. "He is innocent of all the charges. In Tehran, Wang collected documents that were 100 years old. He has told me often of his exhilaration at the exquisiteness and depth of Persian civilization."
The report from Mizan, which included a photo from the Princeton website, also contained a quote from Wang in which he praises the British Institute of Persian Studies for facilitating access to Iran's National Archives and other libraries. The quote was used as evidence of his spying activities, the report said, adding, "Wang admits his mission in Iran."
"I have been having trouble accessing Tehran's archives and libraries," Wang said in the 2015-2016 annual report of the British Institute of Persian Studies, a nonprofit organization based in London.
"Mrs. Reyhanpour offered to help," he said of one of the institute's employees. "And within a few days, she put me in contact with senior scholars at the National Archive. . . . Without Mrs. Reyhanpour's help it would be hard to imagine how long it would have taken for me to become acquainted with academic institutions in Iran."
Wang's reported conviction comes at a particularly tense time for U.S.-Iranian relations, which have rapidly deteriorated since President Trump took office.
Under the previous administration, the United States and other world powers negotiated a deal with Iran to curb its nuclear program in exchange for sanctions relief. It was hailed as a victory for diplomacy and an end to Iran's global isolation.
Since then, the Trump administration has stepped up its anti-Iran rhetoric and placed U.S. participation in the nuclear deal under review. Monday is the deadline for the White House to decide whether to issue a waiver on nuclear-related sanctions against Iran, a provision that is required periodically under the terms of the 2015 nuclear deal. The administration is expected to approve the waiver, despite an internal debate on how to respond to Iran's human rights abuses and support for militant groups such as Hezbollah.
"The Iranian regime continues to detain U.S. citizens and other foreigners on fabricated national-security related changes," a State Department official said in an emailed statement Sunday. Iran is believed to hold a number of foreign nationals, mostly dual citizens of the United States and European countries, but many of their identities have been kept secret.
"We call for the immediate release of all U.S. citizens unjustly detained in Iran so they can return to their families," the State Department official said.
It was unclear how long Wang may have been in Iranian custody, but Mizan reported that authorities arrested him in August 2016 as he was leaving the country. Facebook and LinkedIn pages with Wang's name, photo and similar work and study history indicate he studied at Harvard University from 2006 to 2008 and later worked as a Pashto language interpreter for the International Committee for the Red Cross in Afghanistan.
"We cannot comment more at the present time, except to say that the university continues to do everything it can to be supportive of Mr. Wang and his family," said Day, the Princeton official.
Also Sunday, the brother of Iranian President Hassan Rouhani was detained for unspecified financial crimes, the judicial spokesman said. Hossein Fereidoun is a close adviser to the president and was involved in the negotiations that led to the nuclear deal with world powers. Hard-line conservatives in Iran had long accused him of corruption.
Morello reported from Washington.