Heavy fighting broke out again on Saturday between Thai and Cambodian soldiers, a day after six died in the bloodiest border clash since the UN appealed for a permanent ceasefire in February.
The two neighbours have fought a series of deadly gunbattles in recent years in disputed jungle near ancient temples strung out along the frontier, which has never been fully demarcated, partly because it is littered with landmines.
"Fresh fighting started at around 6am (2300 GMT Friday) with rifles and mortar shelling at the same flash point" as Friday's clash, said a Thai army spokesman in the border region, Colonel Prawit Hookaew.
"We are negotiating to stop the fighting," he said.
Cambodia confirmed the latest outbreak of hostilities.
"The fighting started at 6.15am. It involves artillery shelling," said defence ministry spokesman Chhum Socheat in Phnom Penh.
There were no immediate reports of casualties in Saturday's violence.
Friday's clash was the first serious outbreak of hostilities since February when 10 people were killed in fighting near the 900-year-old Hindu temple Preah Vihear, prompting UN Security Council members to call for a lasting ceasefire.
The latest fighting, which left three soldiers dead on each side on Friday and more than a dozen others wounded, took place near a different group of temples over 100 kilometres away from Preah Vihear.
Indonesia, which holds the rotating chairmanship of the Association of Southeast Asian Nations (ASEAN) regional bloc, called for an immediate end to the violence.
"Indonesia, as current chair of ASEAN, strongly calls for the immediate cessation of hostilities between Cambodia and Thailand," Indonesian Foreign Minister Marty Natalegawa said in a statement released on Friday.
The two sides blamed each other for Friday's clash, which lasted for more than six hours and prompted thousands of villagers to flee the border area.
Ties between the neighbours have been strained since Preah Vihear -- the most celebrated example of ancient Khmer architecture outside Cambodia's Angkor -- was granted UN World Heritage status in July 2008.
The World Court ruled in 1962 that the temple belonged to Cambodia, but both countries claim ownership of a 4.6 square kilometre (1.8 square mile) surrounding area.
Observers say the temple dispute has been used as a rallying point to stir nationalist sentiment in Thailand and Cambodia.
The two countries agreed in late February to allow Indonesian observers in the area near Preah Vihear, but the Thai military has since said they are not welcome and they have yet to be deployed.
Cambodia has called for outside mediation to help end the standoff, but Thailand insists the dispute should be resolved through bilateral talks.
Thailand recently admitted using controversial Dual Purpose Improved Conventional Munitions during the February fighting but insisted it did not classify them as cluster munitions.
The arms are defined as cluster munitions by the global campaign group Cluster Munition Coalition (CMC), which condemned Thailand's use of the weapons.