Thailand's army has accused Cambodia of breaching a newly-signed ceasefire deal reached after weeks of deadly clashes that forced nearly one million people from their homes.

In a statement, the Thai army reported that more than 250 unmanned aerial vehicles (UAVs) were detected flying from Cambodia on Sunday night.

The ceasefire took effect at noon local time on Saturday, with both sides agreeing to freeze current front lines, ban reinforcements, and facilitate the safe return of civilians in border areas.

Seen as a diplomatic breakthrough, the ceasefire followed days of negotiations with assistance from China and the US.

However, following the alleged violations, the Royal Thai Army expressed serious concerns, stating that Cambodia's actions constitute a violation of agreements aimed at reducing tensions. They warned that the release of 18 Cambodian soldiers held in Thailand might need to be reconsidered.

The Thai military stated it would act in accordance if violations of agreements and national sovereignty persist. Cambodia has yet to issue a comment on the situation.

These developments came shortly after China’s Foreign Minister praised the ceasefire as a hard-won achievement, with US President Donald Trump endorsing the rapid conclusion of the truce.

The dispute between Thailand and Cambodia is historical, intensifying after recent incidents involving nationalistic sentiments over disputed territory. Deadly clashes earlier this year resulted in significant casualties and displacement, leading to the fragile ceasefire agreement.