Why are Thailand and Cambodia fighting at the border?

Simmering tensions between Thailand and Cambodia have once again exploded along their shared border, derailing a fragile ceasefire backed by US President Donald Trump.

At least three Thai soldiers and seven Cambodian civilians have been killed since Monday, with the countries accusing one another of starting the violence.

The clashes, which have also seen Thailand launch airstrikes along the border, are the most serious since the ceasefire was agreed in July.

This is not a recent dispute. The argument between Thailand and Cambodia dates back more than a century, when the borders of the two nations were drawn after the French occupation of Cambodia.

Hostilities escalated in 2008, when Cambodia tried to register an 11th Century temple located in the disputed area as a Unesco World Heritage Site. The move was met with heated protest from Thailand.

Over the years there have been sporadic clashes, with soldiers and civilians killed on both sides.

The latest tensions ramped up in May, after a Cambodian soldier was killed in a clash. This plunged relations between the countries to their lowest point in more than a decade.

In the run up to the first bout of fighting in July, both nations had imposed border restrictions. Cambodia banned imports from Thailand, including fruit and vegetables, power supplies and internet services.

Both countries had also strengthened troop presence along the border in recent weeks.

The two sides have given differing versions of what happened.

On Monday 8 December, the Thai army said its troops had responded to Cambodian fire in Thailand’s Ubon Ratchathani Province. It said that a Thai soldier had been killed.

The Thai army said that it had also launched air strikes on military targets along the disputed border.

However, Cambodia’s defence ministry said it was Thai forces that had attacked first, in Preah Vihear province. Cambodia also insisted that it did not retaliate.

The next day, Thailand’s military accused Cambodia of firing rockets and using bomb-dropping drones and kamikaze drones against Thai soldiers, with some rockets reportedly hitting civilian areas.

It later confirmed it had carried out more airstrikes.

Cambodia has also accused Thailand of firing indiscriminately into civilian areas in its border Pursat Province.

Both sides exchanged gunfire, with each claiming the other had triggered the conflict.

It escalated quickly, with Thailand accusing Cambodia of firing rockets and Bangkok carrying out air strikes on Cambodian military targets.

At least 48 people were killed and thousands displaced during five days of fighting.

Trump then intervened and, with the help of Malaysia, negotiated a ceasefire.

The US president later oversaw the signing of what he dubbed “the Kuala Lumpar peace accord” in October. Thailand refused to call it that – instead referring to it as “Joint Declaration by the prime ministers of Thailand and Cambodia on the outcomes of their meeting in Kuala Lumpur”.

Both agreed to withdraw their heavy weapons from the disputed region, and to establish an interim observer team to monitor it.

The next step was supposed to include the release of 18 Cambodian soldiers held in Thailand.

Thailand paused the agreement in November, with Thai Prime Minister Anutin Charnvirakul saying the security threat “has not actually decreased”.

At the time, Cambodia said it remained committed to the terms of the deal.

After fighting broke out again in December, Thailand’s foreign minister Sihasak Phuangketkeow told the BBC the ceasefire was “not working” and that “the ball is in Cambodia’s court”.

However, Cambodia’s former prime minister Hun Sen said it had only returned fire late on Monday, in order to “respect the ceasefire”.

Trump, meanwhile, has called on both sides to respect the agreement, news agency Reuters said.

Where this leads next is unclear.

While there have been serious exchanges of fire in the past, they de-escalated relatively quickly.

Back in July, that was the path our correspondent Jonathan Head thought would be followed again.

However, he warned, there’s a lack of leadership with the strength and confidence to pull back from this confrontation in both countries at the moment.

You can read more of his analysis from earlier in the year here.

For those travelling to Thailand, the UK Foreign Office currently advises against all but essential travel to areas within 50km of the whole border with Cambodia.

For those in Cambodia, it advises against all but essential travel to border areas within 50km of the whole border with Thailand.

You can check the latest travel advice on the Foreign Office site.