Following peace talks in Malaysia on Monday, both sides agreed an unconditional ceasefire would start at midnight to end fighting over a smattering of ancient temples in disputed zones along their 800-kilometer border.

On Tuesday, the Thai military said Cambodian troops "had launched armed attacks into several areas" in "a clear attempt to undermine mutual trust", but said clashes later stopped.

Cambodia's defense ministry spokeswoman Maly Socheata insisted there had been "no armed clashes against each other in any regions".

However, both sides said some morning meetings between rival military commanders along the border -- scheduled as part of the pact -- had gone ahead.

Cambodian leader Hun Manet and Thai acting Prime Minister Phumtham Wechayachai shook hands over the ceasefire deal Monday at peace talks hosted by Malaysia and attended by delegates from the United States and China.

"I saw photos of the two leaders shaking hands," said 32-year-old pharmacy worker Kittisak Sukwilai in the Thai city of Surin -- 50 kilometers from the border.

"I just hope it's not just a photo op with fake smiles -- and that those hands aren't actually preparing to stab each other in the back."

In Cambodia's Samraong city -- 20 kilometers from the frontier -- an AFP journalist said the sound of blasts stopped in the 30 minutes leading up to midnight, with the lull continuing until midday.

"The frontline has eased since the ceasefire at 12 midnight," Cambodian Prime Minister Hun Manet said in a Tuesday morning message on Facebook.

Jets, rockets and artillery killed at least 42 people since last Thursday and displaced more than 300,000 -- prompting intervention from US President Donald Trump over the weekend.

The flare-up was the deadliest since violence raged sporadically from 2008-2011 over the territory, claimed by both because of a vague demarcation made by Cambodia's French colonial administrators in 1907.

"When I heard the news I was so happy because I miss my home and my belongings that I left behind," Phean Neth told AFP at a sprawling camp for Cambodian evacuees on a temple site away from the fighting.

"I am so happy that I can't describe it," said the 45-year-old.

A joint statement from both countries -- as well as Malaysia -- said the ceasefire was "a vital first step towards de-escalation and the restoration of peace and security".

Both sides are courting Trump for trade deals to avert his threat of eye-watering tariffs, and the US State Department said its officials had been "on the ground" to shepherd peace talks.

"I have instructed my Trade Team to restart negotiations on Trade," Trump said in a message on his Truth Social platform, taking credit for the ceasefire deal after it was announced.

"The US and I are still in negotiations," Thailand's Finance Minister Pichai Chunhavajira told reporters on Tuesday. "We're still waiting for the US to decide whether to accept our proposal."

The statement said China also had "active participation" in the talks, hosted by Malaysian Prime Minister and ASEAN bloc chair Anwar Ibrahim in his country's administrative capital, Putrajaya.

Hun Manet thanked Trump for his "decisive" support, while his Thai counterpart Phumtham said it should be "carried out in good faith by both sides".

Each side had already agreed to a truce in principle while accusing the other of undermining peace efforts, trading allegations about the use of cluster bombs and targeting of hospitals.

Thailand says 14 of its soldiers and 15 civilians were killed, while Cambodia has confirmed only eight civilian and five military deaths.

More than 188,000 people have fled Thailand's border regions, while around 140,000 have been driven from their homes in Cambodia.