Thailand has deployed fighter jets against Cambodian military targets along their disputed border, in a dramatic escalation of tensions that threatens to erupt into a broader conflict.

It comes a day after a Thai soldier lost his leg in a landmine explosion, an incident that saw relations between the two South-East Asian neighbours collapse to their lowest level in years.

Thailand’s second regional military command in the northeast said in a post on Facebook that F-16 fighter jets had been deployed. It also claimed to have “destroyed” two Cambodian regional military support units.

Thailand’s Deputy Army spokesperson Colonel Richa Suksuwanont said the airstrikes were aimed only at military targets.

There was no immediate confirmation from the Cambodian side.

Armed clashes between Thai and Cambodian forces had broken out along the disputed border earlier on Thursday, according to military officials, injuring civilians and prompting the evacuation of residents in Thailand.

They began early morning when Thailand’s military said Cambodian troops fired at a Thai army base in an area near the ancient Ta Muen Thom Temple – which lies in disputed territory in the south of Thailand’s Surin province and in Cambodia’s north-west. It said Cambodia had deployed an unmanned drone in front of the temple before sending troops in with weapons.

It also accused Cambodian troops of firing heavy weapons into a civilian area in the nearby Kap Choeng district, in Surin province.

“The attack injured three civilians. Thai authorities have promptly evacuated residents from the area to ensure the safety of lives and property,” the military said in a statement.

A Cambodian Defence Ministry spokesperson said their troops had acted in self-defence after an unprovoked incursion from Thai soldiers.

“Cambodian forces acted strictly within the bounds of self-defence, responding to an unprovoked incursion by Thai troops that violated our territorial integrity,” Lieutenant General Maly Socheata said.

Cambodia’s Prime Minister Hun Manet said in a post on Facebook that Thailand attacked Cambodian army positions at two temple sites in its Oddar Meanchey province, as well as in Cambodia’s Preah Vihear province and Thailand’s Ubon Ratchathani province.

“Cambodia has always maintained a position of peaceful resolution of problems, but in this case, we have no choice but to respond with armed force against armed aggression,” said the Prime Minister.

Hun Manet also called on Cambodian citizens to remain calm.

At least two Thai soldiers were injured on Thursday, Reuters reported, citing a Thai army official.

Two hospitals in Thailand’s Surin province near the site of the clash have begun evacuating patients, according to Thailand’s ministry of public health.

The armed clash comes a day after a second Thai soldier in a week lost his leg to a landmine explosion at a different point along the disputed border.

Five Thai soldiers were injured in the explosion, with the incident prompting Thailand to downgrade its diplomatic relations with Cambodia – recalling its ambassador from Phnom Penh and expelling the Cambodian ambassador.

Thailand also closed parts of its north-eastern border to locals and tourists.

In response, Cambodia announced it has downgraded relations with Thailand “to the lowest level” and ordered all diplomatic staff to return home.

Tensions between the two neighbours had already soured in May, when a Cambodian soldier was killed during a clash between Thai and Cambodian troops in which both sides opened fire in a contested border area of the Emerald Triangle, where Cambodia, Thailand and Laos meet.

The dispute has since had major political consequences for Thailand and stoked nationalist fervour in both countries.

Thailand’s Prime Minister Paetongtarn Shinawatra was suspended from duties earlier this month and could face dismissal after the leak of a phone call she had with Cambodia’s powerful former leader in which she appeared to criticise her own army’s actions in the dispute.

Thailand and Cambodia have had a complicated relationship of both cooperation and rivalry in recent decades. The two countries share a 817km land border – largely mapped by the French while they occupied Cambodia – that has periodically seen military clashes and been the source of political tensions.