The United Nations Security Council is due to hold an emergency meeting on Friday to discuss the ongoing border clashes between Thailand and Cambodia.

A long-running border dispute erupted into intense fighting on Thursday, with violence flaring near two temples on the border between Thailand's Surin province and Cambodia's Oddar Meanchey.

Both countries blame the other for triggering the latest clashes.

While Cambodia fired rockets and shells into Thailand, the Thai military scrambled F-16 jets to hit military targets across the border.

Clashes continue for a second day

The fighting continued for a second day early on Friday, Thai authorities said.

They also claimed that Cambodia was using heavy weapons, including artillery and rockets.

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

Thailand's acting Prime Minister Phumtham Wechayachai warned on Friday that the cross-border clashes "could develop into war."

"We have tried to compromise as we are neighbors, 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.

The Thai Interior Ministry said the death toll on their side had risen to 14. It added that over 100,000 people from four border provinces had been moved to nearly 300 temporary shelters.

Meanwhile, Cambodia confirmed on Friday its first fatality.

A Cambodian provincial official said on Friday that at least one Cambodian civilian was killed and five others injured.

Around 1,500 Cambodian families from Banteay Ampil district in the Oddar Meanchey province near the conflict zone have been evacuated to safety, Meth Meas Pheakdey, a spokesperson for the provincial administration, said on Facebook.

What is the conflict about?

The two nations are locked in disagreement over the Emerald Triangle — an area where the borders of both countries and Laos meet, and home to several ancient temples.

Thailand and Cambodia, which share an 800-kilometer (500-mile) frontier, have been arguing over where the border should be drawn for years.

Dozens of kilometers in several areas are contested.

Fighting broke out between 2008 and 2011, but a UN court ruling in 2013 settled the matter for over a decade.

The current crisis erupted in May after both countries' militaries briefly fired at each other in a relatively small, contested border area that each nation claims as its own.

Both sides said they acted in self-defense. One Cambodian soldier was killed.

While Bangkok and Phnom Penh said afterwards they agreed to de-escalate the situation, tensions have remained high as Cambodian and Thai authorities continued to implement or threaten measures short of armed force.

How did the international community react?

China's Foreign Ministry said it was deeply concerned about the ongoing clashes and would play a constructive role in promoting de-escalation.

"The root of the issue lies in the lingering legacy of Western colonialism, and it now needs to be approached calmly and handled properly," Foreign Minister Wang Yi told ASEAN Secretary-General Kao Kim Hourn in Beijing, according to his ministry.

The United States and France, Cambodia's former colonial ruler, urged an immediate end to the conflict. The US State Department also advised its citizens against travel within 50 kilometers (31 miles) of the Thailand-Cambodia border.

The EU said it was deeply concerned about the clashes and called for dialogue to end the fighting.

Following mediation offers from the US, and China, Bangkok on Friday said it has rejected third-country mediation efforts, but the Foreign Ministry spokesman said they were open to Malaysian mediation.

"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 Balankura told the French AFP news agency.

Edited by: Sean Sinico