At least 35 people have been killed and more than 200,000 displaced since Thursday as the countries fight over a smattering of contested ancient temples.

In an effort initiated by US President Donald Trump, Thailand's acting Prime Minister Phumtham Wechayachai and Cambodia's Prime Minister Hun Manet will meet at 3:00 p.m. in Kuala Lumpur. China is also expected to send a delegation.

Ahead of the talks, Thailand and Cambodia traded fresh fire and accusations.

"We do not believe Cambodia is acting in good faith, based on their actions in addressing the issue," Phumtham told reporters as he departed Bangkok airport.

"They need to demonstrate genuine intent, and we will assess that during the meeting."

Cambodia's defense ministry spokeswoman Maly Socheata said Monday was "the fifth day that Thailand has invaded Cambodia's territory with heavy weapons and with the deployment of a lot of troops".

The previous night, Thailand's military said Cambodian snipers were camping in one of the contested temples, and accused Phnom Penh of surging troops along the border and hammering Thai territory with rockets.

It said fighting was ongoing in seven areas along the rural border region, marked by a ridge of hills surrounded by wild jungle and agricultural land where locals farm rubber and rice.

"The situation remains highly tense, and it is anticipated that Cambodia may be preparing for a major military operation prior to entering negotiations," the Thai military statement read.

On Saturday, Trump said he made a late-night call to both leaders, who had agreed to "quickly work out" a truce.

Cambodian Prime Minister Hun Manet said the summit -- which will be mediated by Malaysian leader Anwar Ibrahim -- was also organized "with the participation of China" -- a key trade and political ally.

"The purpose of this meeting is to achieve an immediate ceasefire, which was initiated by President Donald Trump and agreed to by both prime ministers of Cambodia and Thailand," Hun Manet said.

US Secretary of State Marco Rubio said that US officials "are on the ground in Malaysia to assist these peace efforts", while Anwar told domestic media he would focus on securing an "immediate ceasefire".

Both sides point the finger

Thai King Maha Vajiralongkorn marked his 73^rd birthday on Monday, but a notice in the country's Royal Gazette said his public celebrations scheduled for Bangkok's Grand Palace have been canceled amid the strife. 

Both Thailand and Cambodia have consistently agreed in principle to a truce -- but accused each other of undermining armistice efforts and of firing first.

Trump has threatened both countries with eye-watering levies in his global tariff blitz unless they agree to independent trade deals.

"When all is done, and peace is at hand, I look forward to concluding our trading agreements with both!" he wrote on social media.

But each side has also blamed the other for undermining peace efforts.

Thailand says eight of its soldiers and 14 civilians have been killed, while Cambodia has confirmed eight civilian and five military deaths.

The Thai military said it had returned the bodies of 12 Cambodian soldiers killed in combat.

The conflict has forced more than 138,000 people from Thailand's border regions, and 80,000 have been driven from their homes in Cambodia.

The Cambodian government has also accused Thai forces of using cluster munitions, while Bangkok has accused Phnom Penh of targeting hospitals.

With the conflict enflaming nationalist sentiments, Thailand issued a warning to its citizens to "refrain from any kind of violence, whether in speech or action" against Cambodian migrants living in the country.