Prime Minister Hun Sen on Friday ratcheted up his attacks on the United States, announcing that he had instructed the Immigration Department to check for American “spies” and suggesting the US Embassy pull out its Peace Corps volunteers.

The premier’s anti-US rhetoric has intensified in the past few weeks following the arrest of opposition leader Kem Sokha, a move widely condemned by civil society and foreign governments. Senior government officials have claimed Sokha was receiving US assistance to foment a “colour revolution” in the country.

In response, the US Embassy questioned Cambodia’s commitment to democracy and has denied the claims – based on a 2013 speech given by Sokha – as a “red herring”. This week it also issued a notice to its citizens warning of anti-American rhetoric in Cambodia.

In an unrelated move, the US also imposed visas sanctions on senior Foreign Ministry officials for the Kingdom’s refusal to accept Cambodians living in the US who are slated for deportation due to felony convictions.

Hitting back, the premier last week suspended a programme that assisted the US in finding and repatriating the remains of American soldiers killed during the Vietnam War.

Speaking to workers at Vattanac Industrial Park, Hun Sen said he asked US Ambassador William Heidt to clarify whether the country had assisted Kem Sokha in planning an overthrow of his government, attributing the accusation to Sokha himself.

“I want to ask His Excellency to clarify whether Kem Sokha’s remark was right or wrong, because we have not accused the US, but Kem Sokha was the one who made accusations that US had instructed [him] on the way to topple and to change the [government] like in Yugoslavia and Serbia,” said the premier.

He added that if the accusations were true then it was up to US President Donald Trump and four former presidents to clarify their actions as well.

“[If] Kem Sokha’s remarks are real, then the US government since [George] Bush, [Bill] Clinton, [George] W Bush, [Barack] Obama and Donald Trump have to come to clarify whether they had instructed Kem Sokha like this or not, if the ambassador has no capability to clarify,” he said.

He again resurrected long-held grouses about US support to the Lon Nol regime and its bombing campaign in the early 1970s, and said that the Immigration Department will now investigate US “spies” whom he suspected of being behind the 2013 labour strikes on Veng Sreng Boulevard.

“In the past, we have known about it, and there were two spies who had provided instruction for the Veng Sreng [strikes],” he said.

Hun Sen also characterised the embassy’s travel warning as a terror threat alert, asking the US to share any intelligence on the purported threat, while seemingly ignoring the fact that the statement explicitly referenced “anti-American rhetoric by officials” in the Cambodian government.

If the situation was so dire, Hun Sen said, then the US should pull out its Peace Corp volunteers. “If Your Excellency’s country is suffering the threat of a terrorist attack, this is Your Excellency’s issue and should not scare Cambodians. And it is good if your Excellency then takes your Peace Corps back,” he said.

The suggestion to pull out Peace Corp volunteers came as the embassy was swearing in 71 new recruits.

The US Embassy on Friday declined to comment on the premier’s comments, but Ambassador Heidt, speaking to journalists after the swearing in for new Peace Corp volunteers, said he was unclear of the connection between the embassy’s travel warning and the suggestion for removing the volunteers.

“We do that [security warnings] in every country. Whenever Americans travel overseas they should be careful. We give security training to our volunteers as well and that’s something we take very seriously always as the US government,” he said.

Immigration Department head Sok Phal declined to comment and National Police spokesman Kirth Chantharith could not be reached.