A Thai F-16 fighter jet launched an airstrike on Cambodian territory on Thursday, marking a dramatic escalation in a long-standing border dispute that has now resulted in at least 12 deaths, including 11 civilians, according to both nations.

According to Thailand’s military, they confirmed that one of 6 F-16 fighter jets deployed along the disputed frontier crossed into Cambodian airspace and destroyed a military target.

According to Thai army deputy spokesperson Richa Suksuwanon said that they have used air power against military targets as they have planned earlier.

On the otherhand, Cambodia condemned the action. It further stated that Thai jets dropped two bombs on a road.

The Cambodian defense ministry has described the airstrike as reckless and brutal military aggression and a violation of Cambodian sovereignty and territorial integrity.

In latest details violence follows a sharp deterioration in diplomatic relations. On late Wednesday, Thailand recalled its ambassador from Phnom Penh and announced the expulsion of Cambodia’s envoy in Bangkok.

Thai officials claimed the move occurred after second Thai soldier lost a limb due to landmine that was recently planted in the contested area.

According to the reports of Thai health ministry, 11 civilians including a child and 1 soldier were killed by artillery shelling fired by Cambodian forces.

At least 24 civilians and seven soilders were wounded. Cambodian authorities haven’t confirmed any casualties on their side.

Also, Thai military in a statement condemned Cambodia for targeting civilians. They further stated that Thailand is ready to protect its sovereignty and his people from inhumane actions.

Residents in Thailand’s Surin province took shelter in reinforced bunkers with sandbags and tires located near the border.

A woman told Thai Public Broadcasting Service (TPBS) in response to a reporter’s query that there have been countless round of fires. She further told that gunfire and explosions echoed nearby.

Cambodia’s foreign ministry called Thailand’s airstrikes “unprovoked” and demanded an immediate withdrawal of Thai forces, urging Bangkok to avoid further provocations that could escalate the conflict.

The clashes have drawn concern from regional and global powers. Malaysian Prime Minister Anwar Ibrahim and chairing ASEAN urged both sides to show restraint and announced plans to speak with the leaders of Thailand and Cambodia to seek a peaceful resolution.

China also voiced concern, offering to assist in de-escalation efforts.

Tensions along the 817-km (508-mile) border have simmered for over a century due to unresolved territorial claims.

Sporadic skirmishes have occurred over the years, including a deadly weeklong artillery exchange in 2011.

The current crisis began in May when a Cambodian soldier was killed in a brief gunfire exchange, triggering a diplomatic breakdown that has now spiraled into armed conflict.