Thailand accused Cambodia of violating a 10-day-old truce yesterday, saying cross-border mortar fire wounded a soldier, while Phnom Penh said a "pile of garbage" exploded, injuring two of its own troops.

The Thai military said it warned Cambodian forces to exercise caution, stressing if a similar incident occurred, Thailand may need to retaliate.

A decades-old border dispute between the Southeast Asian nations erupted into military clashes several times last year, with fighting in December killing dozens of people and displacing around one million on both sides.

The two countries agreed a fragile truce on December 27, ending three weeks of clashes.

"Cambodia has violated the ceasefire" yesterday morning, the Thai army said in a statement, accusing Cambodian forces of firing mortar rounds into Thailand's Ubon Ratchathani province.

One Thai soldier was hospitalised due to non-life-threatening shrapnel wounds to his right arm, the army said. The Thai army said in a separate statement that the Cambodian side had contacted a Thai military unit and claimed "there was no intention to fire into Thai territory".