Three Cambodian and two Thai soldiers were killed on Friday after fighting erupted on the countries' disputed border, according to officials on both sides.
"Some of our soldiers were injured and three died in the clash," Cambodian defence ministry spokesman Chhum Socheat said in Phnom Penh.
The Thai military said two of its soldiers had died and seven others were injured.
Both sides accused each other of starting the fighting with small arms fire and artillery shells. The violence shattered a two-month lull in long-standing tensions on the border.