Prime Minister Hun Sen again lashed out at the US Embassy in Phnom Penh, alleging it was the “mastermind” of opposition leader Kem Sokha’s purported “treasonous plot” and questioning its nascent social media campaign highlighting the US’s positive engagement in the Kingdom.

Anti-US rhetoric has reached a fever pitch following the jailing of Cambodia National Rescue Party President Kem Sokha after an old video was recently circulated showing him saying he had received assistance from the United States to plan his political career. He has since been charged with “treason”.

Government mouthpiece Fresh News has also pumped out unverified stories, mostly from anonymous readers and Facebook users, alleging that US-funded NGOs – including the recently expelled National Democratic Institute – were part of a conspiracy to overthrow the Cambodian government.

The premier continued this line of attack yesterday, saying the US was looking to “destroy” the country by being the “initiator” and “mastermind” supporting the “puppet”, a thinly veiled reference to Sokha. He also resurrected long-held grouses with the US over its bombing campaign in the early 1970s and an outstanding Lon Nol-era debt.

Some “2.7 million tonnes of bombs have not yet been completely dealt with”, Hun Sen said. “[They] attacked us and [then] demand money from us,” he added, declaring the irony “delicious”.

“And this group is the one who destroys, is the initiator, who is the mastermind, and its puppet is in Cambodia.”

Hun Sen also took umbrage with former US Ambassador William Todd’s flashing a peace sign – which was interpreted as a confusing cultural faux pas – after a meeting of lawmakers with King Norodom Sihamoni in 2013. Mimicking the gesture yesterday, Hun Sen called Todd a “gangster”, and took a swipe at the embassy’s attempts to be a “parent” to Cambodia.

“We cannot accept such a diplomatic attitude. And I hope that such things won’t happen in the attitudes of other diplomats,” he said, speaking at a graduation ceremony for medical students.

Meanwhile, the US Embassy on Friday launched the hashtag “#RedHerringsKH”, using a term for misleading information designed to distract people from relevant issues – an apparent reference to the ongoing furore surrounding its purported collusion with Sokha.

It has since published three Facebook posts with the hashtag, all titled “What does the United States do in #Cambodia?” The three posts described the embassy’s efforts to protect 2.6 million hectares of forest, preserve temples and improve reading levels among primary school students.

“What does the United States do in Cambodia? We save temples!” one post reads, ending with an admonition to “Watch out for #RedHerringsKH”.

The campaign seemed to have caught the attention of Hun Sen, who asked, “Why is your Facebook posting a fish and interpreting [the situation] differently?”

The embassy said it had no comment yesterday.

Ou Virak, founder of local think tank Future Forum, said while past attacks on the US had been mostly sporadic, the recent push to link the country to an anti-government conspiracy was “overboard”, and could provoke pushback.

“They [the US] are sending a subtle message. They want the government to understand the message.”

Human Rights Watch’s Phil Robertson said the attacks on the US would falter, no matter “how loudly or strongly Typhoon Hun Sen howls”, and “the Cambodian people will end up picking up the mess and paying the bills, just like [they] always have to do”.