Thai and Cambodian soldiers have clashed along the two countries' border in a major escalation of a festering dispute over territory that killed least 14 people, mostly civilians.

SURIN, Thailand (AP) — Thai and Cambodian soldiers have clashed along the border between their countries in a major escalation that left at least 14 people dead, mostly civilians. The two sides fired small arms, artillery and rockets, and Thailand also launched airstrikes.

Fighting took place in at least six areas on Thursday, according to Thai Defense Ministry spokesperson Surasant Kongsiri, a day after a land mine explosion along the border wounded five Thai soldiers and led Bangkok to withdraw its ambassador from Cambodia and expel Cambodia’s envoy to Thailand.

On Friday, Cambodia’s chief official in Oddar Meanchey province, Gen. Khov Ly, said clashes resumed early in the morning near the ancient Ta Muen Thom temple. Associated Press reporters near the border could hear sounds of artillery from early morning hours.

The official also said that at least four civilians were wounded in Thursday’s fighting there and that more than 4,000 people have been displaced from their villages along the border to evacuation centers. It was the first account of any casualties from the Cambodian side.

The escalation represents a rare instance of military conflict between member countries of the Association of Southeast Asian Nation, though Thailand has tangled with Cambodia before over the border and has had sporadic skirmishes with western neighbor Myanmar.