Fighting raged Thursday along the border of Cambodia and Thailand, with explosions heard near centuries-old temples ahead of US President Donald Trump's planned phone call to the leaders of both nations.
At least 19 people have been killed in the latest round of border fighting that reignited last week, officials said.
More than half a million people, mostly in Thailand, have fled border areas near where jets, tanks and drones have waged battle, AFP reported.
The Southeast Asian nations dispute the colonial-era demarcation of their 800-kilometer (500-mile) frontier, where both sides claim a smattering of historic temples.
This week's clashes are the deadliest since five days of fighting in July that killed dozens before a shaky truce was agreed, following intervention by Trump.
The US president said he expected to speak Thursday with the leaders of Thailand and Cambodia to demand a halt to the clashes.
"I think I'm scheduled to speak to them tomorrow," Trump told reporters at the White House on Wednesday.
Speaking to journalists on Thursday, Thai Prime Minister Anutin Charnvirakul said there had been "no coordination" yet with Trump.
"But if there's a call from the US president, we definitely will answer the phone and we will explain to him... He does not have more details of the situation than me," Anutin said.
"This is an issue between two countries. He has good intentions to see peace but we have to explain what the problems are and why it turned out this way," the prime minister added.
Both sides blame the other for reigniting the conflict, which has expanded to five provinces of both Thailand and Cambodia, according to an AFP tally of official accounts.
In Thailand's northeast on Thursday morning, hundreds of evacuated families woke inside a university building in Surin city that has been transformed into a shelter.
A few older women pounded chilli paste while volunteers stirred big pots of food.
Nearby, 61-year-old farmer Rat, who declined to give her last name, said she had to leave her home before she could plant a cassava crop this season, fleeing with her family of eight.
"I just want to go home and farm again," she told AFP.
"Every time the fighting starts, it feels like life gets paused all over again."
- Cultural heritage -
Nine Thai soldiers have been killed this week and more than 120 wounded, Thai defense ministry spokesperson Surasant Kongsiri told reporters on Thursday.
"The operation is still ongoing across the border from Ubon Ratchathani down to Trat province," Surasant said
Cambodia's defense ministry has reported 10 civilian deaths and 60 wounded.
AFP journalists in Cambodia's northwestern Oddar Meanchey province heard blasts of incoming artillery from the direction of disputed temples from dawn on Wednesday.
Cambodia's defense ministry said in a statement that Thai forces initiated an attack early Thursday morning in the province, "shelling into Khnar Temple area".
On the other side of the border, the Thai military announced an overnight curfew from 7:00 pm to 5:00 am in parts of Sa Kaeo beginning Wednesday night.
The Thai army said Wednesday that Cambodian forces fired rockets earlier that day that landed in the vicinity of the Phanom Dong Rak Hospital in Surin province -- to the north of Sa Kaeo, and which was struck in the fighting in July.
Cambodia's defense ministry said more than 101,000 people have been evacuated, while in Thailand, authorities said more than 400,000 civilians have taken shelter elsewhere.
The United States, China and Malaysia, as chair of the regional bloc ASEAN, brokered a ceasefire back in July.
In October, Trump backed a follow-on joint declaration, touting new trade deals with Thailand and Cambodia after they agreed to prolong their truce.
But Thailand suspended the agreement the following month.
The United Nations cultural agency called Wednesday for "protection of the region's cultural heritage in all its forms".
It added that it was concerned about the hostilities near the Temple of Preah Vihear, a UNESCO heritage site.
In 2008, military clashes between Thailand and Cambodia erupted over a patch of land next to the 900-year-old temple, located on the border.
Sporadic violence from 2008 to 2011 led to the deaths of two dozen people and displacement of tens of thousands.
