Thailand has accused Cambodia of placing land mines in a disputed border area after three soldiers were injured, but Phnom Penh denied the claim and said the soldiers had veered off agreed routes and triggered a mine left behind from decades of war.

Thai authorities said the three soldiers were injured, with one losing a foot, by a land mine while on a patrol on July 16 on the Thai side of the disputed border area between Ubon Ratchathani and Cambodia's Preah Vihear province.

Cambodia's foreign ministry denied that new mines had been planted, and said in a statement on Monday night that the Thai soldiers deviated from agreed patrol routes into Cambodian territory and into areas that contain unexploded land mines. The country is littered with land mines laid during decades of war.