A long-running border dispute erupted into intense fighting with jets, artillery, tanks and ground troops on Thursday, and the UN Security Council is set to hold an emergency meeting on the crisis later Friday.

A steady thump of artillery strikes could be heard from the Cambodian side of the border Friday, where the province of Oddar Meanchey reported one civilian -- a 70-year-old man -- had been killed and five more wounded.

More than 138,000 people have been evacuated from Thailand's border regions, its health ministry said, reporting 15 fatalities -- 14 civilians and a soldier -- with a further 46 wounded, including 15 troops.

"We have tried to compromise as we are neighbours, but we have now instructed the Thai military to act immediately in case of urgency," said Wechayachai.

"If the situation escalates, it could develop into war -- though for now, it remains limited to clashes," he told reporters in Bangkok.

Fighting resumed in three areas around 4:00 am on Friday (2100 GMT Thursday), the Thai army said, with Cambodian forces firing heavy weapons, field artillery, and BM-21 rocket systems, and Thai troops responding "with appropriate supporting fire".

- 'Deeply distressing' -

By the afternoon, foreign ministry spokesman Nikorndej Balankura told AFP there were signs the fighting was easing off, and said Thailand was open to talks, possibly aided by Malaysia.

"We are ready, if Cambodia would like to settle this matter via diplomatic channels, bilaterally, or even through Malaysia, we are ready to do that. But so far we have not had any response," Nikorndej told AFP.

Malaysia currently holds the chair of the Association of Southeast Asian Nations (ASEAN) regional bloc, of which Thailand and Cambodia are both members.

Chinese Foreign Minister Wang Yi said casualties were "deeply distressing" and called for the crisis to be "approached calmly and handled properly".

Cambodia has stayed tight-lipped about its casualty numbers, but AFP journalists saw four wounded soldiers and three civilians receiving treatment at a hospital in Oddar Meanchey.

The soldiers said they were injured during the fighting on Thursday, while the civilians said they were hit by shrapnel.

In the Cambodian town of Samraong, 20 kilometres (12 miles) from the border, AFP journalists saw families speeding away in vehicles with their children and belongings as gunfire erupted.

"I live very close to the border. We are scared," Pro Bak, 41, told AFP.

He was taking his wife and children to a Buddhist temple to seek refuge.

- Long-running dispute -

The fighting marks a dramatic escalation in a long-running dispute between the neighbours -- both popular destinations for millions of foreign tourists -- over their shared 800-kilometre (500-mile) frontier.

Dozens of kilometres in several areas are contested and fighting broke out between 2008 and 2011, leaving at least 28 people dead and tens of thousands displaced.

A UN court ruling in 2013 settled the matter for over a decade, but the current crisis erupted in May when a Cambodian soldier was killed in a new clash.

Fighting on Thursday was focused on six locations, according to the Thai army, including around two ancient temples.

Ground troops backed up by tanks battled for control of territory, while Cambodia fired rockets and shells into Thailand and the Thais scrambled F-16 jets to hit military targets across the border.

Both sides blamed each other for firing first, while Thailand accused Cambodia of targeting civilian infrastructure, including a hospital hit by shells and a petrol station hit by at least one rocket.

burs-pdw/dhc