Thailand’s acting Prime Minister Phumtham Wechayachai on Friday warned that the clashes could “move towards war”.
He said the fighting now included heavy weapons and had spread to 12 locations along the border.
Thailand also accused Cambodia of firing into civilian areas and evacuated all villages deemed to be within the radius of its rockets.
Cambodia, for its part, accused Thailand of using cluster munitions. Cluster munitions are banned in much of the world because of their indiscriminate effect on civilian populations. Thailand has not responded to the allegations.
Meanwhile, Thailand’s foreign minister told the Reuters news agency there was “no need” for third-party mediation in the conflict, even as global leaders appealed for an immediate ceasefire.
Malaysian Prime Minister Anwar Ibrahim, who chairs the Association of South East Asian Nations (Asean), had earlier offered to facilitate talks between the two countries.
The US also called for an “immediate cessation of hostilities, protection of civilians and a peaceful resolution of the conflict”.