BANGKOK (AP) — Thailand launched airstrikes along the disputed border with Cambodia on Monday as both sides accused the other of attacking first.

Tensions have simmered since the Southeast Asian neighbors signed a truce agreement in October pushed by U.S. President Donald Trump after their territorial disputes led to five days of combat in July that killed dozens of soldiers and civilians.

Thai army spokesperson Maj. Gen. Winthai Suvaree said the Cambodian troops fired first into Thai territory in multiple areas. He said one Thai soldier was killed and four other soldiers were wounded, and civilians were being evacuated from the affected areas.

Thailand used aircraft “to strike military targets in several areas to suppress Cambodian supporting fire attacks," he said.

Cambodian Defense Ministry spokesperson Maly Socheata said the Thai military attacked the Cambodian troops first. She said Cambodia did not retaliate during the initial attacks Monday.

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

The Cambodian Education Ministry said several schools along the border were ordered closed Monday. Photos and videos posted on its Facebook page showed young students running out of classes to their parents. Some rode on a motorcycles and others were seen walking away hurriedly.

A brief firing incident along the border occurred Sunday. The Thai army said Cambodia fired first and injured two Thai soldiers. It said the Thai troops retaliated, resulting in an exchange of fires for around 20 minutes. Cambodia however said the Thai side fired first and that it did not retaliate.

The U.S.-brokered ceasefire that ended the brief conflict was threatened last month after Thai troops were injured by land mines, leading Thailand to announce that it would indefinitely suspending the implementation of the agreement. Both sides continue to trade accusations over responsibility, even as they are supposed to be cooperating in getting rid of the mines.

Trump said in mid-November he'd stopped a war between them as the tensions simmered.

Thailand and Cambodia have a history of enmity going back centuries, when they were warring empires.

Their modern territorial claims stem largely from a 1907 map drawn when Cambodia was under French colonial rule, which Thailand has argued is inaccurate.

The International Court of Justice in 1962 awarded sovereignty to Cambodia over an area that included the 1,000-year-old Preah Vihear temple, which still rankles many Thais.

The ceasefire does not spell out a path to resolve the underlying basis of the dispute, the longstanding differences over where the border should run.