Thailand launched airstrikes along its disputed border with Cambodia on Monday morning, the Thai military said, with both countries accusing each other of restarting the conflict.

Thai Prime Minister Anutin Charnvirakul, in a televised speech, said that military operations would continue as necessary to defend the country and protect public safety.

"Thailand has never wished for violence. I'd like to reiterate that Thailand has never initiated a fight or an invasion, but will never tolerate a violation of its sovereignty," he said.

Why are Thailand and Cambodia fighting again?

The Royal Thai Army accused Cambodian forces of attacking Thai troops in the Sisaket province on December 7, injuring two soldiers.

It went on to report further attacks on Sunday night into Monday morning, calling it a "significant incident," in which it said one Thai soldier was killed and eight wounded. It also said a civilian community had been targeted.

In a social media post, the military said there had been another clash in Ubon Ratchathani Province on Monday morning, which prompted the airstrikes.

Thai Army spokesperson Winthai Suvaree said that aircraft had been deployed in response "to strike military targets in several areas to suppress Cambodian supporting fire attacks."

Troops were also deployed to evacuate residents from the area, the military said.

Cambodia rejected the Thai side of the story, with Defense Ministry spokesperson Maly Socheata saying Thai forces had launched an attack on Cambodian troops in the border provinces of Preah Vihear and Oddar Meanchey early Monday morning, adding that Cambodia had not retaliated.

"Cambodia urges that Thailand immediately stop all hostile activities that threaten peace and stability in the region," she said.

Meanwhile, Cambodia's information minister told French news agency AFP that at least four civilians had died in Monday's skirmish.

"At least four Cambodian civilians were killed in the Thai attacks" in the border provinces of Oddar Meanchey and Preah Vihear, said Neth Pheaktra, adding that 10 other civilians were wounded.

UN and EU urge restraint

Both the United Nations and the European Union have urged restraint.

UN Secretary-General Antonio Guterres called on "both parties to exercise restraint and avoid further escalation" and urged both Thailand and Cambodia to "recommit to the ceasefire" brokered earlier this year.

"The recent exchange of fire between Cambodia and Thailand is an escalation in hostilities," said an EU spokeswoman, adding: "The EU calls on both countries to exercise maximum restraint and return to the Joint Declaration signed on 26 October, and the confidence-building measures set out therein."

What happened to the Trump-backed Thai-Cambodia ceasefire?

A ceasefire was brokered by US President Donald Trump and Malaysian Prime Minister Anwar Ibrahim back in October following a five-day war in July that led to the displacement of hundreds of civilians on both sides.

Tensions continued to simmer, resulting in Thailand saying in mid-November it would indefinitely suspend the implementation of the agreement after Thai soldiers were injured by land mines, they said were laid by Cambodia. Despite Trump saying he would intervene to avoid further tensions, the future of the ceasefire remains uncertain.

On Monday, Malaysian Prime Minister Ibrahim called for restraint in a statement posted to social media, sharing with it an image of Thai and Cambodian leaders signing a peace agreement in October.

"Malaysia stands ready to support steps that can help restore calm and avert further incidents. Our region cannot afford to see long-standing disputes slip into cycles of confrontation," Ibrahim wrote.

The clashes between Thailand and Cambodia are connected to a decades-old dispute over colonial-era borders.

The two countries share an 800-kilometer (500-mile) border stretching across sparsely inhabited regions that are home to several temples both countries claim as their own.

This includes the historic Preah Vihear temple, a 1,000-year-old Hindu site built by the Khmer Empire.

Although a 1962 ruling by the International Court of Justice determined that the temple was located in Cambodian territory, competing claims largely stem from a 1907 map drawn when Cambodia was under French colonial rule. Thailand has argued that this map is inaccurate.

Edited by: Dmytro Hubenko