At least 14 people were killed during clashes along the disputed land between Cambodia and Thailand, according to Thai authorities.
Thailand's interior ministry also said it had evacuated over 100,000 people from four border provinces as the deadly clashes entered a second day.
Thailand’s army said most of the casualties were civilians from three Thai provinces, while Cambodia has yet to confirm whether it suffered any casualties.
As well as the dozen fatalities reported, authorities said 32 people were injured.
“We condemn this – using heavy weapons without a clear target, outside of conflict zones … the use of force and did not adhere to international law,” Thailand’s acting prime minister, Phumtham Wechayachai, told reporters.
“We remain committed to peaceful means and there should be discussions, but what happened was a provocation and we had to defend ourselves.”
Following the conflict, Thailand has closed its border with Cambodia, and Cambodia has downgraded its ties with Thailand, accusing its military of using “excessive force”.
Both Thailand and Cambodia have given different accounts of how the most recent conflict broke out and urged citizens to evacuate to safer locations.
This marked the bloodiest military clash between the two South-East neighbours in over a decade.
