Both Thailand and Cambodia face a steep 36 per cent tariff on their exports to the United States, as part of Trump’s trade war. The US is Thailand’s biggest export customer. Earlier this week, Thailand said it was close to reaching a deal with the US that would see the tariff rate cut in exchange for allowing greater market access to US agricultural and industrial products.

Thailand and Cambodia have faced off since the killing of a Cambodian soldier late in May during a brief skirmish. Troops on both sides of the border were reinforced amid a full-blown diplomatic crisis that brought Thailand’s fragile coalition government to the brink of collapse.

Donald Trump speaks to reporters in Scotland on Friday. Credit: Getty Images

The tensions erupted on Thursday at as many as eight locations along the border, where sovereignty has been ambiguous for more than a century.

Small arms fire escalated to heavy shelling of military targets on both sides, and Thailand said Cambodian rockets had also hit civilian areas, including a hospital. Phnom Penh said a Thai F-16 jet had bombed a road near the famous Preah Vihear Temple.

At least 19 people – mostly civilians – have been killed so far in Thailand, while Cambodia said on Saturday that 12 more people had died on its side, bringing its toll to 13. Dozens of others have also been reported injured in the fighting.

Both sides have now sought diplomatic support to end the conflict, saying they had acted in self-defence and calling on the other to cease fighting and start negotiations.

Displaced Cambodians receive water at the Battkhao Resettlement Camp in Oddar Meanchey Province on Saturday as a border clash entered its third day.Credit: AP

Thailand’s ambassador to the U.N. told an emergency meeting of the Security Council – called by Cambodia and held behind closed doors late on Friday in New York – that soldiers had been injured by landmines in Thai territory on two occasions since mid-July and that Cambodia had then launched attacks on Thursday morning. Cambodia has stated the landmines were leftovers from previous conflicts.

“Thailand urges Cambodia to immediately cease all hostilities and acts of aggression, and resume dialogue in good faith,” Cherdchai Chaivaivid told the council in remarks released to media.

Cambodia has strongly denied the claims. Its defence ministry said Thailand had launched the “deliberate, unprovoked, and unlawful military attack” on Thursday, and was now mobilising troops and military equipment on the border.

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“These deliberate military preparations reveal Thailand’s intent to expand its aggression and further violate Cambodia’s sovereignty,” the ministry said in a statement on Saturday.

Cambodia’s UN ambassador Chhea Keo told reporters after the security council meeting that his country had “asked for immediate ceasefires, unconditionally, and we also call for the peaceful solution to the dispute”.

He responded to accusations that Cambodia attacked Thailand, asking how a small country with no air force could attack a much larger country with an army three times its size, stressing, “We do not do that.”

Bangkok has reiterated it wanted to resolve the dispute bilaterally, telling the Security Council it was “deeply regrettable that Cambodia has deliberately avoided meaningful dialogue and instead sought to internationalise the issue to serve its own political objectives”.

Cambodia has also expressed outrage at Thailand’s use of cluster munitions, calling it a violation of international law.

Thailand’s military, however, said the country was not a party to the Convention on Cluster Munitions but that it followed the principle of proportionality, “to enhance explosive destruction capabilities against military targets only”.

The Security Council did not issue a statement, but a diplomat said all 15 members called on the parties to de-escalate, show restraint and resolve the dispute peacefully.

The council also urged the regional bloc, the Association of South-East Asian Nations – known as ASEAN – to help resolve the border fighting, the diplomat said, speaking on condition of anonymity because the meeting was private.

Malaysia, which chairs the 10-nation regional bloc that includes both countries, called for an end to hostilities and offered to mediate.

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Australia and Britain have issued travel advisories to avoid certain areas of Cambodia and Thailand, including the border regions of Buriram, Si Sa Ket, Surin, and Ubon Ratchathani provinces.

As the fighting intensified, villagers on both sides have been caught in the crossfire, leading many to flee.

About 600 people took shelter at a gymnasium in a university in Surin, Thailand, some 80 kilometres from the border. Evacuees sat in groups, on mats and blankets, and queued for food and drinks.

Seamstress Pornpan Sooksai was accompanied by four cats in two fabric carriers. She said she was doing laundry at her home near Ta Muen Thom temple when shelling began on Thursday.

“I just heard, boom, boom. We already prepared the cages, clothes and everything, so we ran and carried our things to the car. I was frightened, scared,” she recalled.

Rattana Meeying, another evacuee, said she had also lived through the 2011 clashes between the two countries but described this flare-up as worse.

“Children, old people, were hit out of the blue,” she said. “I never imagined it would be this violent.”

In the Kantharalak district of Thailand’s Sisaket province, on the border near some of the clashes, hotel worker Chianuwat Thalalai said the town had emptied.

“Nearly everybody’s gone, it’s almost a deserted city,” the 31-year-old told Reuters. “My hotel is still open for some of those nearer to the border area that need a place to stay.”

Across the border in Cambodia, villages on the outskirts of Oddar Meanchey province were largely deserted. Homes stood locked, while chickens and dogs roamed outside.

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Some villagers earlier dug holes to create makeshift underground bunkers, covering them with wood, tarpaulin and zinc sheets to shield themselves from shelling. Families with children were seen packing their belongings on homemade tractors to evacuate, though a few men refused to leave.

A remote Buddhist temple surrounded by rice fields accommodated several hundred evacuated villagers. Women rested in hammocks, some cradling babies, while children ran about. Makeshift plastic tents were being set up under the trees.

Veng Chin, 74, pleaded with both governments to negotiate a settlement “so that I can return to my home and work on the farm.”

Thailand and Cambodia have bickered for decades over the position of the line of demarcation along their 817-kilometre land border, with ownership of the ancient Hindu temples Ta Moan Thom and the 11th century Preah Vihear central to the disputes.