|The two sides had agreed on a truce following fighting on Saturday over the disputed border area [Reuters]
Thai and Cambodian soldiers have exchanged gunfire at a disputed area of land around the site of a 900-year-old Hindu temple.
Sunday's clash is the third in three days around the temple - known as Preah Vihear in Cambodia and Khao Phra Viharn in Thailand - despite a ceasefire declared by Thai officials a day earlier.
Wayne Hay, Al Jazeera's correspondent, reporting from the Thai-Cambodia border, confirmed the fighting.
"We can see the artillery fire streaming across the night sky ... [and] we've seen some ambulances heading towards the area," he said.
The AFP news agency quoted a Cambodian military commander as saying: "We are fighting now, they [Thai troops] started firing at us first."
But Colonel Sunsern Kaewkumnerd, a Thai army spokesman, accused the Cambodian side of reigniting the violence.
There were no immediate reports of casualties but later Cambodian authorities said that part of the temple had been damaged by fire from the Thai side of the border.
Although sporadic clashes in the area are not unusual, it is rare for the two sides to fight over consecutive days.
A Thai soldier was killed on Saturday as Thai and Cambodian troops fought with rocket-propelled grenades and guns, prompting residents to flee the area.
A truce was reached in the early afternoon.
Saturday's violence followed an intense two-hour clash on Friday in which three Cambodians, including two soldiers, and a Thai villager were killed, the first fatalities in the militarised border area since a Thai soldier was shot dead in January last year.
Following Friday's violence, the Thai foreign ministry accused Cambodia of engaging in "an act of aggression" in "violation of Thai sovereignty and territorial integrity".
Cambodia accused Thailand of invasion and filed a complaint with the UN Security Council.
Southeast Asia's regional grouping Association of South East Asian Nations (ASEAN), of which both Thailand and Cambodia are members, said the deteriorating situation was undermining confidence in the region and would affect its economic development and investment prospects.
The temple has been a source of tension for generations, with observers saying it is used as a rallying point to stir nationalist sentiment in both Thailand and Cambodia.
The International Court of Justice awarded it to Cambodia in 1962 but the ruling did not determine the ownership of the scrub next to the ruins, leaving considerable scope for disagreement.