Thai officials say 12 have been killed in Cambodian shelling, as neighbours trade fire and accusations of blame.

Fighting erupts along disputed Thailand-Cambodia border

A Thai F-16 fighter jet has bombed targets in Cambodia, as a simmering border dispute and diplomatic meltdown rapidly ignited into fierce clashes, bombing and shelling that have killed at least 11 civilians and a soldier in Thailand.

Thailand and Cambodia each blamed the other for the new outbreak of fighting that erupted early Thursday in an area near the disputed Ta Moan Thom Temple, located in a border area in northwestern Cambodia’s Oddar Meanchey province.

Fighting then spread to at least six areas along the border, Thai military official Rear Admiral Surasant Kongsiri said, leading Thailand’s military to close the border between the countries.

Amid regional calls for mediation, Thailand’s caretaker Prime Minister Phumtham Wechayachai told a press conference that fighting had to stop before there could be any negotiations. He said there had been no declaration of war, and that the fighting was not spreading to further provinces.

Thailand’s Health Minister Somsak Thepsuthin said 11 Thai civilians, including an 8-year-old boy, and a soldier had been killed in artillery shelling by Cambodian forces. He said 24 civilians and seven military personnel had been wounded.

The health minister told reporters that Cambodia’s actions, including an attack on a hospital, should be considered war crimes.

A Thai military statement detailing the casualties said six civilians had been killed and two wounded in shelling near a petrol station in Ban Phue, Kantharalak district, Sisaket province, about 20km (12 miles) from the border.

Other casualties included two civilians, including the 8-year-old boy, killed in an attack near the Ban Chorok area, Kabcheing district, Surin province which wounded two others. Another person was killed and one wounded in Nam Yuen district, Ubon Ratchathani province, the statement said.

The fighting has led to the evacuation of at least 40,000 civilians from 86 villages near the border to safer locations, a district official in Surin province told the Reuters news agency, as residents fled to bomb shelters built of concrete and fortified with sandbags and car tyres.

Cambodia has made no statement about any casualties on its side.

Cambodian Prime Minister Hun Manet has requested an urgent meeting of the United Nations Security Council in response to the violence, saying it “gravely threatened peace in the region”.

Both countries issued statements accusing the other of instigating the fighting that erupted early Thursday near a disputed temple, following weeks of heightened tension between the neighbours.

Thailand’s military said that, early on Thursday, Cambodia had deployed a surveillance drone before sending troops to the area, who they said had opened fire with heavy weapons, including artillery and long-range BM21 rockets, forcing Thai soldiers to retaliate.

Thailand’s military said six F-16 fighter jets had been readied to deploy in the border conflict, and that their raids had hit two “Cambodian military targets on the ground”, according to Thai military deputy spokesperson Ritcha Suksuwanon.

In a situation deteriorating by the hour, Cambodian forces launched attacks on civilian areas in Thailand, including a hospital, causing deaths, Thailand’s Ministry of Foreign Affairs said.

Cambodia’s Ministry of National Defence said the Thai jets dropped two bombs on a road, and that it “strongly condemns the reckless and brutal military aggression of the Kingdom of Thailand against the sovereignty and territorial integrity of Cambodia”.

The Cambodian ministry also accused Thailand of attacking first and violating an agreement designed to de-escalate tension, saying its troops had acted in self-defence after coming under attack.

Cambodia’s influential former prime minister, Hun Sen, said in a post on social media that Thailand’s military had shelled two Cambodian provinces bordering Thailand, Oddar Meanchey and Preah Vihear, adding that “the Cambodian army has no choice but to fight back and counterattack”.

He also called for the public to remain calm and not panic-buy rice and other food supplies.

Thailand has announced school closures in some regions, while Cambodia also said it had evacuated students and teachers from affected areas.

The fighting has drawn expressions of concern from other Asian countries, who called for a halt to the violence.

Malaysian Prime Minister Anwar Ibrahim, the current chair of the ASEAN bloc of southeast Asian countries to which Thailand and Cambodia belong, called for calm and said he would speak to leaders of both countries on Thursday evening to push for a peaceful resolution.

“The least we can expect is for them to stand down and hopefully try to enter into negotiation,” said Anwar.

At a briefing, a spokesperson for China’s Ministry of Foreign Affairs, Guo Jiaku, also expressed Beijing’s deep concern about the situation, saying it hoped both sides would address their issues through dialogue. He said China would play a constructive role in promoting de-escalation.

Reporting from Koh Lanta, southern Thailand, Al Jazeera’s Tony Cheng said the dispute “has been simmering for some time, but it seems to have exploded today”.

“There was a feeling up until today that this was a game of pressure, waiting to see who would crack first,” he said. “We hadn’t seen a lot of actual exchanges of fire over the border – but today, that all changed.”

He said the fighting had its origins in a longstanding dispute over the border drawn between the countries by the French during Cambodia’s colonial era, in regions where there had been relatively free movement of people back and forth for generations.

The dispute has dragged on for decades, flaring into deadly military clashes more than 15 years ago, and then again in May, when a Cambodian soldier was killed in a firefight further to the north of the conflict areas.

In recent weeks, tensions surged again after Thai soldiers were severely injured by land mines that the Thai military says were newly laid by Cambodian forces on the Thai side of the border. Meanwhile, Cambodia announced that it would begin military conscription from next year.

Cheng said nationalist sentiment was surging on both sides, with strongman Hun Sen – the former Cambodian prime minister and father of the current prime minister – “right at the heart of” whipping up tensions in his country over the dispute.

Thailand and Cambodia have for more than a century contested sovereignty at various undemarcated points along their 817km (508-mile) land border.

The latest skirmishes broke out after Thailandrecalled its ambassadorto Cambodia late on Wednesday, and said it would expel Cambodia’s envoy, after a second Thai soldier in a week lost a limb to a landmine that Bangkok claimed had been recently laid by Cambodia in the disputed area. In response, Cambodia said it would withdraw all of its diplomats from Thailand, and ordered all Thai diplomats to leave.

Cambodia has denied planting mines, and claims that Thai soldiers have veered off agreed paths and triggered mines left behind from Cambodia’s civil war.