SAMRONG ? Cambodian and Thai troops exchanged heavy weapons fire for the third straight day on Sunday, officials from both countries said, after clashes on their joint border left 10 dead.

A Cambodian field commander, Suos Sothea, said the fighting started at about 10:00 am local time (0300GMT) and both sides were firing mortars.

"What we can confirm is it involves artillery shell fire," he said.

A Thai official at the border also confirmed the resumption of hostilities and said "Cambodian opened fire first".

UN Secretary-General Ban Ki-moon has said the neighbors should "exercise maximum restraint" and urged the pair to launch "serious dialogue" in order to resolve the issue, according to a spokesman.

Six Cambodian troops and four Thai soldiers have been killed in the latest fighting.