Continued cross-border clashes between Thai and Cambodian troops caused damages to a disputed 11th Century temple (map, from bbcimg.co.uk), which is a UN World Heritage site.
Cambodian officials said that part of Preah Vihear temple collapsed after a Thai bombardment, Thailand has not commented.
Since Friday five people died in the fighting and thousands of villagers have been evacuated.
Tension increased in the region since 2008, when Cambodia won World Heritage status for the temple.
Even though the temple’s main entrance is in Thailand, in 1962 an international ruling said it belonged to Cambodia. Both countries claim the surrounding area.
“A wing of our Preah Vihear temple has collapsed as a direct result of the Thai artillery bombardment,” said the Cambodian military commander, in a statement.
This month a court ruling sparked the most recent tension. Two members of a Thai nationalist movement were sentenced by a Cambodian court to up to eight years in prison after finding them guilty of espionage.
The two were among seven Thai politicians and activists charged with illegal entry after crossing into the disputed border area in December.
Mortar, rocket and artillery fire were reportedly involved in Sunday’s flare-up which began around 1835 local time (1135 GMT).
Despite at least two ceasefires, fighting has continued, with both sides blaming each other for breaking the ceasefires.
A Cambodian military commander told AFP news agency : “We are fighting now, they started firing at us first.”
But the news agency also quoted Thai Col Sunsern Kaewkumnerd as saying : “Thailand has retaliated. The fighting is still going on. There are no reports of casualties.”
According to Thai PM Abhisit Vejjajiva’s weekly address, the army and government officials from both countries are working “to normalise the situation”.