Prime Minister Hun Sen took time out from a speech ostensibly about labour rights yesterday to revisit old grievances with the US – slamming it for its destructive role in Cambodia before the Khmer Rouge takeover, and even inviting Ambassador William Heidt to personally inspect two chemical bombs unearthed in Svay Rieng province earlier this year.

The premier’s words are the latest jabs at the US government, which finds itself at the centre of a political crackdown that has seen US-backed independent radio stations closed, the American-funded National Democratic Institute kicked out and opposition leader Kem Sokha jailed on “treason” charges – allegedly for conspiring with the US to topple the government. The only evidence the government has produced of the purported collusion is a 2013 video in which Sokha says the US helped him to hone his political message.

Those tensions were compounded by friction over the US’s controversial deportation of Cambodian felons residing on its soil. Cambodia’s recent hesitation in accepting the deportees prompted the US to ban visas for certain Foreign Ministry officials. On Tuesday, the Cambodian government responded by formally suspending cooperation in repatriating the remains of American soldiers who died in the country during the Vietnam War.

The premier addressed the issue again yesterday, saying the US only cared about recovering the remains of its fallen soldiers and recuperating outstanding debt accrued during the Lon Nol regime.

The premier has repeatedly criticised the US for not forgiving its debts, which total more than $500 million, citing the damage inflicted on the country through bombing and its role in supporting the corrupt Lon Nol regime. “If it is possible, not only take the bones, but also help bring the remaining bombs in Cambodia back to the US,” Hun Sen said.

“[The US] thinks only about getting the money back . . . but for the bombs, they don’t want it back; they just advise [Cambodia] to follow democracy. When they came to kill Cambodians, they did not talk about democracy,” added the premier, himself a former member of the Khmer Rouge, which was targeted by US bombing in the early 1970s.

The US Embassy declined to comment yesterday, but referred to a statement from Heidt earlier this month, in which he said the US is “committed” to addressing its war era legacy, and has provided over $160 million to this end.

“Half of that money has gone to clearing ordnance dropped by US planes . . . But the other half has gone to clearing Chinese, Soviet and Vietnamese mines in the west – minefields that are 10 times more deadly,” the statement said.

The prime minister yesterday specifically mentioned two chemical bombs uncovered in Svay Rieng province’s Romeas Hek district in January that have yet to be moved. The drums contain CS, a type of tear gas.

Hun Sen claimed the chemical could cause serious health problems to villagers, and could even cause deformities in exposed children. No research has linked tear gas to birth defects, but a Post investigation in Svay Rieng province last month found deformities consistent with exposure to Agent Orange, a chemical defoliant used by the US during the Vietnam War. “It is the responsibility of the US. It cannot be ignored. You come and create problems for others,” Hun Sen said.

Cambodia Mine Action Centre President Heng Ratana wrote yesterday on Facebook that America had a “duty” to assist Cambodia to remove the bombs because both countries are signatories to the Organisation for the Prohibition of Chemical Weapons (OPCW), which has prohibited CS as “a method of warfare”.

“If a State Party considers that a [riot control agent] has been used against it as a method of warfare, it has the right to request assistance from the OPCW,” according to the body’s website.

Ly Thuch, secretary-general of the Cambodia Mine Action and Victim Assistance Authority, said Cambodia may do just that. “We are open to meeting the organisation to see how we could deal with the problem,” he said.

The OPCW did not respond to requests for comment.

However, Ear Sophal, an associate professor of diplomacy and world affairs at Occidental College, said the current criticism of the US was unfair and politically motivated.

“How much have the Chinese, Russians and Vietnamese given to demining in Cambodia? Why no criticism of these three? Ah, and why no criticism of the debt owed to the Russians which is actually . . . three times what Cambodia owes the US!” he said via email.