Simmering tensions between Thailand and Cambodia have once again exploded along the 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 both sides accusing each other of starting the violence.

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

On that occasion, at least 48 people were killed, and thousands were displaced following 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".

Just two weeks later, Thailand suspended the deal. Then, in December, fighting broke out once again.

So, how did we get here - and where is it going?

This is not a recent dispute. In fact, 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.

Things officially became hostile in 2008, when Cambodia tried to register an 11th Century temple located in the disputed area as a Unesco World Heritage Site - a move that was met with heated protest from Thailand.

Over the years there have been sporadic clashes that have seen 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 bilateral ties to their lowest point in more than a decade.

In the run up to the first bout of fighting in July, both countries had imposed border restrictions on one another. Cambodia banned imports such as fruits and vegetables from Thailand, and also stopped importing power 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, that it said had killed a hai soldier.

It added that it had launched air strikes on military targets along the disputed border.

Phnom Penh's defence ministry said it was the Thai forces that attacked first, in Cambodia's Preah Vihear province. Cambodia also insisted that it did not retaliate.

The next day, Thailand's military accused Cambodia of using multiple-launch rocket systems, 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.

Again, both sides gave different versions of what happened.

Thailand's National Security Council (NSC) claimed that just after 07:30 local time (00:30GMT) on 24 July, Cambodia's military deployed drones to conduct surveillance of Thai troops near the border.

Shortly afterwards, it said, Cambodian military personnel carrying rocket-propelled grenades gathered near the border. Soldiers on the Thai side attempted negotiations by shouting, but were unsuccessful, the NSC spokesman claimed, adding that Cambodian soldiers opened fire at around 08:20, forcing the Thai side to retaliate.

Thailand also accused Cambodia of deploying heavy weapons, including BM-21 rocket launchers and artillery, causing damage to homes and public facilities including a hospital and a petrol station along the Thai side of the border.

Meanwhile, Cambodia alleged that Thai soldiers initiated the conflict at around 06:30, when they violated a prior agreement by advancing on a Khmer-Hindu temple near the border and placing barbed wire around its base.

Thai soldiers then deployed a drone just after 07:00, and fired shots "into the air" at around 08:30, according to Maly Socheata, a spokesperson from Cambodia's Ministry of National Defence.

At 08:46, Thai soldiers "pre-emptively" opened fire on Cambodian troops, leaving them no choice but to exercise their right to self-defence, according to the Phnom Penh Post newspaper quoting Socheata.

Socheata further accused Thailand of deploying excessive troops, using heavy weapons and carrying out air strikes on Cambodian territory.

Thailand had already paused the agreement back 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, Bangkok's foreign minister Sihasak Phuangketkeow told the BBC the ceasefire was "not working" - adding "the ball is in Cambodia's court".

However, Cambodia's former prime minister Hun Sen said they had only returned fire late on Monday, in order to "respect the ceasefire".

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

Under the terms of the agreement signed in October, the two countries 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.

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 British Foreign Office currently advises against all but essential travel to border areas within 50km of the whole border with Cambodia.

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