That second blow to the paper’s independence came quickly. Hours after it published online an article about Mr. Sivakumar’s company, Asia PR, representatives of the publisher appeared in The Post’s newsroom and demanded that the article be removed.
“The first thing they said was to take the article down, right now,” said Ananth Baliga, one of the article’s authors.
Stuart White, the managing editor; Brendon O’Byrne; the business editor; Jenni Reid, the web editor; and Mr. Baliga all refused to comply and resigned.
The paper’s editor in chief, Kay Kimsong, also refused and was dismissed.
In a statement, Mr. Sivakumar blasted The Post’s editorial staff as “careless and vicious” and called the article a “disgrace,” adding that it “smells of malice.”
For a quarter-century, as the United States and Europe helped Cambodia rebuild from the ravages of the genocidal rule of the Khmer Rouge, they tied billions of dollars in aid to an effort to transform Cambodia into a liberal democracy. But Mr. Hun Sen has relied increasingly in recent years on China’s political and financial support.
The country is nominally democratic, but Mr. Hun Sen, the longest-ruling leader in Asia, has recently shuttered dissenting news outlets, jailed dozens of critics and dissolved the main opposition party, the Cambodia National Rescue Party, or C.N.R.P. — apparently with Beijing’s blessing.
“With or without the sale, press freedom in Cambodia is close to nonexistent,” said Kem Monovithya, the opposition party’s deputy director general of public affairs and the daughter of its leader, Kem Sokha, who was detained in September and accused of plotting a United States-funded coup — a charge he denies.
Sam Rainsy, the former leader of the opposition party, who abruptly quit last year in the face of government pressure, said that The Post had recently published two of his letters to the editor, but that he did not expect the new management to continue the practice.
“The prospects were already very bleak for a free and fair election” in July, Mr. Sam Rainsy added in a telephone interview from Paris, where he lives in exile. “But the disappearance of The Phnom Penh Post as an independent newspaper makes those prospects even worse.”
More than 20 members of The Post’s staff issued a statement expressing “disgust for this decision made in contradiction to the values of a free press that our hardworking staff have upheld since 1992.”
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“Our article was written in an attempt to maintain the transparency and integrity of our paper as we have done for more than 25 years,” they wrote.
The Post’s sale may indicate that Mr. Hun Sun’s administration has decided that it no longer needs to allow a free media to operate in the country as a concession for getting Western aid, said Shawn Crispin, the Bangkok-based Southeast Asia representative for the Committee to Protect Journalists, a nonpartisan advocacy group based in New York.
“Now China is its main patron, and they have no such interests,” he said.
Mr. Crispin said he worried that the tax bill The Post was facing might have been a pressure tactic used to force the newspaper’s previous owner, Bill Clough, to sell, rather than fight the bill in court.
In a video uploaded by The Phnom Penh Post last year, Mr. Clough said that the newspaper’s independence and loyal following were its “major distinguishing factor” and that his staff was “remarkably free” from government interference.
Huy Vannak, an Interior Ministry official, said that the prime minister was “too busy doing the affairs of the nation” to concern himself with the sale of a newspaper, adding that he was unaware of any prior business relationship between Mr. Hun Sen and Mr. Sivakumar’s company.
The newspaper’s new owner, Mr. Sivakumar, is the chief executive of Asia PR, a Malaysian firm based in Kuala Lumpur. Its website says, without elaborating, that Mr. Hun Sen’s “entry into the government seat” was among its government-related projects.
The website for Asia PR offers a service to political clients it calls “covert PR,” in which it promises to “exploit and explain an issue to prove that the politician is good.”
The paper’s new ownership said on Sunday in a statement that it was “fully committed” to upholding the 26-year-old newspaper’s “principles/independence without infringing any relevant laws and regulations of the Kingdom of Cambodia,” The Post reported.
But Mr. Sophal Ear, the analyst, said he saw the language about obeying laws as “a signal to the authorities” about the newspaper’s future. “I think the odds are greater than 50/50 the paper’s coverage will change — and for the worse,” he said.
Asia PR’s website calls Mr. Sivakumar “a journalist by discipline and training from the United Kingdom and Australia” who was previously editor in chief of The Eastern Times, a newspaper in the Malaysian state of Sarawak. His personal assistant, Krishna Kumar, said Monday in an email that he was unavailable for comment and would be out of the office for about two weeks.