Cambodian officials say two soldiers have been killed and two wounded in clashes with Thailand Wednesday along a disputed stretch of the border between the two countries.
Cambodian officials say the gunfight lasted for about an hour. It broke out near an ancient religious temple that is at the center of the dispute.
Thailand's military says five of its troops were wounded in the fighting. Each side says the other fired first.
It was not immediately clear how many soldiers were involved.
Earlier Wednesday, Thai air force official Captain Montol Suchookorn said Thai fighter planes have been put on standby to provide support for troops stationed along the border. He also says transport planes are ready to evacuate Thai nationals from Cambodia.
Tensions escalated Tuesday when Cambodian Prime Minister Hun Sen demanded Bangkok withdraw its troops from the area within 24 hours, or face what he called a "life and death battleground."
He alleged that 84 Thai soldiers crossed about one kilometer inside Cambodia on Monday.
Thailand said its troops were on patrol.
The countries have long disputed the ownership of the 900-year-old Preah Vihear temple and nearby areas. In 1962, the International Court of Justice granted sovereignty of the temple to Cambodia, but the adjacent land remained under Thai control.
Thailand initially supported Phnom Penh's bid to have the Hindu temple declared a UNESCO (United Nations Educational, Scientific and Cultural Organization) World Heritage site. But the government backed off after intense protests by opposition protesters.
UNESCO named the Preah Vihear temple as a World Heritage site in July.
Some information for this report was provided by AFP and AP.