Clashes between Thai and Cambodian troops took place along their border for a second day early on Friday, with Cambodia using heavy weapons including artillery and rockets, Thailand's military said.

"Cambodian forces have conducted sustained bombardment utilising heavy weapons, field artillery and BM-21 rocket systems," it said. "Thai forces have responded with appropriate supporting fire in accordance with the tactical situation."

The Thai interior ministry said more than 100,000 people from four border provinces had been moved to nearly 300 temporary shelters, while the health ministry announced that the death toll had risen to 14 – 13 civilians and one soldier.

The 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 on Friday.

In the Cambodian town of Samraong, 20 kilometres from the border, distant artillery fire could be heard early on Friday.

Soldiers could be seen rushing to man rocket launchers and speeding off towards the frontier.

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 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 Bangkok accused Phnom Penh of targeting civilian infrastructure, including a hospital hit by shells and a petrol station hit by at least one rocket.

Thursday's clashes came hours after Thailand expelled the Cambodian ambassador and recalled its own envoy after five members of a Thai military patrol were wounded by a landmine.

Cambodia downgraded ties to "the lowest level" on Thursday, pulling out all but one of its diplomats and expelling their Thai equivalents from Phnom Penh.

China and the EU said they were "deeply concerned" about the clashes, calling for dialogue. The United States urged an "immediate" end to the conflict, while Cambodia's former colonial ruler France made a similar call. (AFP/Reuters)