Cambodia's prime minister on Sunday said the country would halt all fuel imports from neighbour Thailand, as tensions escalate over an ongoing border dispute.

The nations have been at loggerheads since a Cambodian soldier was killed last month as troops exchanged fire in a disputed area known as the Emerald Triangle, where the borders of both countries and Laos meet.

"Starting from midnight tonight, all fuel and gas imports from Thailand will be halted," Cambodian leader Hun Manet wrote on social media.

He said energy companies would be able to "import sufficiently from other sources to meet domestic fuel and gas demands" in the country.

Thailand has placed restrictions on several border checkpoints citing "national security", and on Sunday Cambodia closed two crossings in retaliation.

In statements issued on Sunday, Cambodia's foreign ministry urged citizens not to travel to Thailand unnecessarily, while Thailand's consular affairs department warned Thais in Cambodia to avoid "protest areas".

The border spat has triggered political turmoil in Thailand after a phone call between leaders was leaked, prompting domestic criticism of Thai Prime Minister Paetongtarn Shinawatra's conduct.

The ruling Thai party's biggest coalition partner withdrew earlier this week as calls grew louder for her to step down and she was forced to apologise over her phone conversation with former Cambodian leader Hun Sen.

Thailand was Cambodia's third-biggest trading partner in 2022, according to the World Bank, with imports reaching US$3.8 billion, of which fuels accounted for 27 percent.

Earlier on Sunday, Cambodia's defence ministry accused the Thai army of violating an agreement by escorting some 150 cyclists to visit a disputed temple near the border.

The Thai army denied any violation, saying there had been a "misunderstanding". (AFP)