Thailand has said it has carried out air strikes on Cambodian military targets along the two countries' disputed border. It called it a response to an attack by Cambodian troops.
According to Thai sources, two Thai soldiers were killed, and four others were wounded on Sunday.
Cambodia has denied that its troops attacked the Thais. It has insisted that the Thais attacked first and that the Cambodians refrained from retaliating.
The border dispute between Cambodia and Thailand has a long history, and the latest escalation occurred in July, when fighting on the border lasted for five days and claimed dozens of lives.
The sides then signed a ceasefire agreement brokered by Malaysia. US President Donald Trump has also joined these efforts. He called the leaders of both countries and threatened to break off tariff negotiations with them unless the fighting stopped.