Hun Sen’s Cambodian People's Party won local elections in June, although the opposition Cambodia National Rescue Party fared reasonably well, increasing expectations of a close contest in the general election.
Hun Sen directed much of his anger at the English-language Cambodia Daily newspaper, saying it had to pay taxes accrued over the past 10 years by Sept. 4 or face closure.
"Pay taxes to the state if you want to exist. If you don't pay taxes, pack your bag and leave," Hun Sen said in a speech at a ceremony in Phnom Penh.
He called the daily "thief chief".
The Cambodia Daily was founded by an American journalist in 1993 and has come in for criticism from the government at times over years for coverage of issues such as corruption, human rights and the environment.
The paper's general manager, Douglas Steele, issued a statement in which he did not refer to the demand for tax but expressed his hope to "fast forward through the current political theatrics".
"If the prime minister is using this as a pretext for a political decision to close down the free press before next year's elections, is it shocking that a politician would do politics?" Steele asked.
Fresh News, a pro-government news outlet, leaked a letter on Aug. 4 from the finance ministry ordering the newspaper to pay $6.3 million in back taxes, penalties and interest within a month or face the seizure of its assets and closure.
Hun Sen also attacked the United States and NGOs.
"The Americans invaded Iraq and Iraqis died, why hasn't the US been punished?" he said. "The Americans brought trouble to Libya, Syria, Yemen, why aren't the Americans punished?"
Arend C. Zwartjes, public affairs officer at US Embassy in Cambodia, declined to comment.
Hun Sen also criticized NGOs and the European Union for funding a consortium of election monitoring groups that criticized some aspects of the June local elections.
Hun Sen's opponents accuse him of using various measures including legal action and intimidation to silence critics and undermine the opposition ahead of the general election.