Thailand’s army on Monday accused Cambodia of violating a newly signed ceasefire agreement, just a day after it came into effect following weeks of deadly border clashes.

In a statement, the Royal Thai Army said it detected more than 250 unmanned aerial vehicles flying from the Cambodian side on Sunday night. It said the move amounted to provocation and breached measures meant to ease tensions.

The ceasefire took effect at noon on Saturday. Under the deal, both sides agreed to freeze troop positions, stop reinforcements and allow displaced civilians in border areas to return home as soon as possible.

Thai army officials said Cambodia’s actions were not in line with the agreement and warned that Thailand may reconsider the release of 18 Cambodian soldiers held since July. The army said it would be forced to act if violations and threats to national sovereignty continue.

Cambodian Foreign Minister Prak Sokhonn downplayed the issue, describing it as a minor matter involving drone flights observed by both sides along the border, according to AFP.

The accusation came hours after China’s Foreign Minister Wang Yi praised the ceasefire as hard-won, while US President Donald Trump welcomed its swift conclusion.

Thailand and Cambodia have a long-running border dispute dating back more than a century. Tensions rose earlier this year after incidents near a disputed temple and escalated in May when a Cambodian soldier was killed.

Five days of intense fighting later left dozens of soldiers and civilians dead and forced large numbers of people to flee their homes. A ceasefire agreed in July and signed in October collapsed earlier this month after fresh clashes, with both sides blaming each other.

With inputs from BBC