In a vaguely worded explanation, Singapore's government expelled a prominent Chinese-born American academic from the country.
It's an unusual move for the city-state, which reportedly may not have taken the step for decades.
Huang Jing, who had been granted permanent residency in Singapore, was high profile: He was the director of the Centre on Asia and Globalisation, a professor at the Lee Kuan Yew School of Public Policy and an independent director on the board of property player Keppel Land.
But on Friday, Singapore's Ministry of Home Affairs said in a press release that Huang was an "undesirable immigrant," for engaging in "activities inimical to Singapore's national interests."
The MHA alleged that Huang had knowingly interacted with intelligence organizations and agents of a foreign country and worked with them to influence Singapore's government policy and public opinion in the city-state by offering "prominent and influential Singaporeans" what he described as "privileged information."
The press release said Singapore's government declined to act on that information, without providing details of the information or what country Huang was alleged to have cooperated with.
The MHA said Huang's wife, Shirley Yang Xiuping, would also be expelled for being aware of her husband's alleged actions. After leaving the country, both will be permanently barred from re-entry, the MHA said.
Huang denied the allegations in comments to the South China Morning Post over the weekend. Reuters reported on Tuesday that Huang and his wife, who were still in Singapore, have appealed the decision.
"It's nonsense to identify me as 'an agent of influence'for a foreign country," he said, according to SCMP. "And why didn't they identify which foreign country they're referring to? Is it the U.S. or China?"
"How can they treat me like this? If they have evidence, they should take me to court," he added, according to the SCMP report.
James Chin, director of the Asia Institute at the University of Tasmania, said it was "quite normal" for countries to not provide a formal reason for expelling a noncitizen.
He said it wasn't the first time Singapore had taken that step, pointing to the city-state's move to expel a U.S. diplomat in the late 1980s.
In that incident, Singapore had expelled a U.S. diplomat it accused of meeting with "dissidents" to encourage them to campaign against the ruling party.
Chin said Huang's alleged actions, although not the details were disclosed, might not have been unusual in other countries, but may have concerned authorities in the city-state.
"It is taken for granted that there is no such thing as academic freedom in Singapore. In other countries, an academic being involved in policy is normal," he said. "In Singapore, it's unacceptable."
Chin hypothesized that Huang was acting on behalf of the U.S., saying there were rumors the actions were related to the Association of Southeast Asian Nations (ASEAN) meetings held over the weekend.
But he added that any storm would likely pass over quietly as long as whoever Huang was working with didn't offer any official confirmation.
The MHA declined to comment when CNBC requested more details about the expulsion and how often it takes that measure.
It's not clear that Huang, who wrote for China state-owned publication Global Times, would have acted on behalf of the U.S.
In an op-ed in the Global Times, published in June, Huang said the current U.S. government was in a "state of chaos," but he warned that impeaching U.S. President Donald Trump would "ignite" internal conflicts there.
In that column, Huang added that China's President Xi Jinping was showing "China's sense of reasonability as an emerging major power."
Huang has resigned from the board of Keppel Land, the property developer said in a filing with the Singapore stock exchange.
His profile has been removed from the website of the Lee Kuan Yew School of Public Policy.
Over the weekend, a National University of Singapore spokesperson told the Straits Times that Huang had been suspended without pay.
"This is a matter of serious concern, and LKYSPP is cooperating fully with MHA," an NUS spokesperson said in a statement provided to CNBC. "NUS does not tolerate such acts of foreign interference, even as we continue to value and uphold the diverse and international character of our University. As this matter relates to national security, the University is unable to comment on the details of the case."
Last year, Huang also briefly gained some local notoriety when a taxi driver alleged the professor had asked him to step out of the taxi and "show some respect;" when the driver refused, Huang allegedly refused to exit the car, according to a local media report.
The driver called the police, who advised the two to "keep the peace," local online publication The Independent reported at the time.