Thailand evacuated more than 100,000 people along the Cambodian border, it said on Friday, as the two countries fight their bloodiest military clashes in over a decade.

The interior ministry said 100,672 people from four border provinces had been moved to shelters, while the health ministry announced the death toll had risen to 14.

Why are Thailand and Cambodia engaged in a border conflict?

Thailand scrambled an F-16 fighter jet to bomb targets in Cambodia on Thursday after artillery volleys from both sides killed at least 11 civilians.

Both blamed each other for starting a morning clash at a disputed area of the border, which quickly escalated from small arms fire to heavy shelling in at least six locations 209km (130 miles) apart along a frontier where sovereignty has been disputed for more than a century.

On Friday morning, the Thai army said in a statement that clashes started at 4am in the border areas of Chong Bok and Phu Makhuea in Ubon Ratchathani Province, as well as in Phanom Dong Rak District, Surin Province. It said Cambodian forces were using heavy weapons including artillery and rockets and that Thai forces were responding.

The worst fighting between the countries in 13 years came after Thailand on Wednesday recalled its ambassador to Phnom Penh and expelled Cambodia’s envoy in response to a second Thai soldier losing a limb to a landmine that Bangkok alleged had been laid recently by rival troops, an accusation Cambodia called baseless.

Thailand said there were 14 fatalities, including an eight-year-old boy. Authorities said 31 people were hurt on Thursday.

“We condemn this – using heavy weapons without a clear target, outside of conflict zones … the use of force and did not adhere to international law,” Thailand’s acting prime minister, Phumtham Wechayachai, told reporters.

“We remain committed to peaceful means and there should be discussions, but what happened was a provocation and we had to defend ourselves.”

Thailand’s health minister, Somsak Thepsuthin, said a hospital was hit by shelling in Surin province, an attack he said should be considered “a war crime”.

Cambodian government, defence and foreign ministry officials gave no indication of fatalities sustained or any estimate of the number of people evacuated.

The UN security council was due to meet on Friday over the conflict.

The US, a longtime treaty ally of Thailand, called for an immediate end to hostilities.

“We are … gravely concerned by the escalating violence along the Thailand-Cambodia border and deeply saddened by reports of harm to civilians,” the state department’s deputy spokesperson, Tommy Pigott, told a regular news briefing.

“The United States urges an immediate cessation of hostilities, protection of civilians and a peaceful resolution of the conflict.”

Britain’s foreign ministry on Thursday advised against all but essential travel to parts of Cambodia and Thailand.

With Agence France-Presse and Reuters