A ceasefire agreed between Thailand and Cambodia took effect at midnight (1700 GMT Monday), temporarily halting heavy fighting along their shared border, though Thai authorities reported violations by Cambodian forces in several areas briefly afterwards.
The Thai military said on social media platform X that "the Cambodian side violated the ceasefire agreement, with disturbances and weapon attacks found in multiple areas."
"The Thai side responded to the situation by deploying frontline forces and using supporting weapons to suppress the Cambodian military operations," it added.
Cambodia's Defence Ministry, by contrast, said the situation remained calm.
The leaders of both South-East Asian nations had met in Malaysia on Monday and agreed to an "immediate and unconditional" ceasefire after days of deadly clashes over a long-simmering border dispute.
The talks were brokered by Malaysian Prime Minister Anwar Ibrahim and included representatives from the United States and China.
A planned meeting between military officials from Thailand and Cambodia was postponed by several hours on Tuesday morning, with no explanation provided.
The cross-border violence, which erupted on Thursday along the more than 800-kilometre border, has left people dead and injured on both sides, many of them civilians. More than 200,000 people have been displaced. Each side blames the other for sparking the clashes, and the exact cause of the escalation remains unclear.
US President Donald Trump had previously urged both governments to halt the fighting, warning that planned US tariffs - set to take effect in early August — would not be lifted unless hostilities ceased.
After the meeting in Malaysia, Trump wrote on Truth Social: "I am pleased to announce that, after the involvement of President Donald J. Trump, both Countries have reached a CEASEFIRE and PEACE."
