3, Kem Sokha, president of the opposition Cambodia National Rescue Party and a member of parliament, was arrested for alleged treason. "It's an act of treason with conspiracy with foreign country, betraying his own nation, this requires arrest", Hun Sen said.
Tension has been growing in the Southeast Asian country in the run-up to a general election next year in which the opposition party has been expected to challenge Hun Sen's rule of more than three decades.
Mr Kem Sokha's daughter Monovithya Kem said her father was taken away handcuffed after a raid by between 100 and 200 policemen without an arrest warrant.
"This paper takes special pride in writing about some of the toughest issues", she told Reuters as journalists polished their final articles and office workers packed everything they could into cardboard boxes.
The opposition party made no immediate comment on the veracity or content of the video.
The party of Kem Sokha, who police detained during a midnight raid on his Phnom Penh home, denied the allegations and said the charges were politically motivated.
Hun Sen, 65, was first installed as Cambodia's prime minister in 1985 during the Vietnamese occupation of the country.
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Transgender service members have also filed suit in federal court to challenge the directive. ". The ACLU is suing the Trump administration over the ban, as are Lambda Legal and OutServe .
The opposition party lost to Hun Sen's Cambodian People's Party in local elections in June, but it did well enough to increase expectations of a close contest in the 2018 vote.
The European Union called for his immediate release, based on the fact that he is meant to have parliamentary immunity, as an elected lawmaker. If Kem Sokha is found guilty of any offence, it could allow the government to shut the party under a new law. USA non-profit the National Democratic Institute and at least one other US charity were expelled from the country. Earlier in the year, it suspended joint military exercises with the United States, which has voiced fears over the human rights situation.
"This government move follows a number of troubling recent steps, including the imposition of unprecedented restrictions on independent media and civil society".
The government appeared to have based part of its claims against Kem Sokha on a video clip that shows the opposition leader giving a public speech in which he describes a grassroots political strategy to challenge Hun Sen with United States support.
The country's tax department announced in early August that the Cambodia Daily, an independent English-language newspaper, owes some $6 million in unpaid tax from 2007 to 2016, and ordered the publisher to pay in full by September 4.
An independent newspaper, The Cambodia Daily, has been ordered to halt publishing by Monday because of a tax dispute, and at least 15 radio stations have been ordered to stop broadcasting programming from the Voice of America and Radio Free Asia.
"It's our livelihood, our mission and our passion to put out the news, but it's a small part of what's going on in Cambodia today", said Jodie DeJonge, The Daily's editor in chief.