BANGKOK - Fighting between Thailand and Cambodia spread to more parts of their contested border on Tuesday, forcing a mass exodus of civilians as the renewed hostilities derailed a US-brokered truce.
READ: Cambodia says Thai troops kill one in fresh border clashes
At least 10 soldiers and civilians have been killed on both sides in the latest spate of fighting, officials said, while more than 140,000 civilians have fled the areas near where jets, tanks and drones were waging battle.
Thailand and Cambodia dispute the colonial-era demarcation of their 800-kilometre frontier, where competing claims to historic temples can spill over into armed conflict.
This week's clashes are the deadliest since five days of fighting in July that killed dozens before a shaky truce was agreed, in large part owing to intervention by US President Donald Trump.
Both sides blame each other for sparking the renewed clashes, which on Tuesday expanded to five provinces of both Thailand and Cambodia, according to an AFP tally of official accounts.
Cambodia's influential former leader Hun Sen said his country retaliated against Thailand, after Phnom Penh said it had initially not fired back for two days as Thailand announced air strikes and tank barrages.
"When is this going to stop?" pleaded Thai farmer Samlee Tahan, 56, who has stayed behind at her rural home in the border province of Surin to guard her livestock.
"I want this to end already," she said.
The Thai army said three soldiers have been killed and 29 wounded since Monday, while Cambodia's defence ministry said seven of its civilians have been killed and about 20 wounded.
In a statement, US Secretary of State Marco Rubio called for "the immediate cessation of hostilities, the protection of civilians, and for both sides to return" to the truce agreement.
- 'Fourth time fleeing' -
The deal was announced after Trump's highly-publicised intervention, as well as more low-key efforts by China and Malaysia -- current chair of the Association of Southeast Asian Nations.
Trump flew to Kuala Lumpur in October to proudly oversee the signing of a follow-on deal to wind down troop deployments, welcome ceasefire monitors and expedite demining efforts.
Cambodian Prime Minister Hun Manet said he nominated Trump for the Nobel Peace Prize, while Trump touted the armistice as one of eight conflicts he had "ended" in his first eight months back in power.
Thailand last month paused the pact's implementation, accusing Cambodia of laying fresh mines in disputed areas.
But this week's violence marks the most major backslide yet.
Fighting has forced Cambodian civilian Poan Hay, 55, to again flee shelling and fighter jets howling above her border home in Oddar Meanchey province.
"It is my fourth time fleeing," she told AFP from a pagoda shelter 70 kilometres from the border.
"I don't know when I can return," she said.
"I want the international community to help Cambodia and tell Thai soldiers to stop."
More than 21,000 people have been displaced from three Cambodian border provinces, Phnom Penh said.
Thailand said more than 125,000 civilian evacuees were camping out in 500 makeshift shelters.
- Shots in the dark -
UN Secretary-General Antonio Guterres on Monday urged both sides "to exercise restraint and avoid further escalation" and "recommit to the ceasefire."
But Phnom Penh accused Thai forces of overnight shelling killing two people traveling on a national road and launching dawn attacks -- including near the flashpoint temple of Preah Vihear.
A grenade attack around the ornate sandstone Preah Vihear, a UNESCO world heritage site, killed one Thai soldier on Tuesday, a Thai army statement said, while indirect fire killed another in Surin province.
Thai Prime Minister Anutin Charnvirakul told reporters his country's military would remain resolute.
"Thailand must stand firmly behind those who protect our sovereignty. We cannot stop now," he said.
Thai navy spokesperson Parat Rattanachaiphan said at a press conference that troops had detected Cambodian soldiers, settlements and several weapon bases in a disputed coastal area of Trat province.
Parat accused Cambodia of deploying drones to provoke Thai forces and said early on Tuesday they "launched a military operation to drive them out."
In Thailand's Surin province, food shop worker Sutida Pusa, 30, shuttles between a temporary shelter where her young and elderly relatives were moved to, and her house where other family members guard their property.
She told AFP on Monday that "the sounds of fighting aren't as loud" as clashes earlier this year.
But "we never trust the situation," she warned.
By Suy Se With Montira Rungjirajittranon In Bangkok