Developments on Sunday threw into doubt Trump’s claims of an immediate push for a ceasefire. The Thai army said Cambodian soldiers opened fire starting in the early morning at a temple, a checkpoint and civilian residences. An army statement said it “necessitated Thai military retaliation to protect Thai citizens and territory, employing long-range artillery to target Cambodian artillery and rocket launchers”.

Cambodia countered that Thailand was the first to attack in the early hours of Sunday morning. “These deliberate and coordinated acts of aggression occurred despite ongoing efforts led by President Donald Trump to broker a ceasefire,” said Cambodia’s defence ministry, adding that Trump’s efforts were “publicly and unequivocally supported” by Cambodia’s prime minister.

Cambodia and Thailand’s border dispute dates back more than a century to disagreements over colonial-era maps. Tensions have been running high since May, when a Cambodian soldier was killed in a brief exchange of fire, but escalated further this week when Thai solders were injured by landmines, which Thai officials claimed had been freshly planted – an allegation Cambodia has denied.