Armed clashes broke out between Thailand and Cambodia along a disputed area of their border on Thursday, both countries said, accusing each other of firing the first shots after weeks of simmering tension and diplomatic spats.

The clash came after Thailand recalled its ambassador to Cambodia late on Wednesday and said it would expel Cambodia’s envoy in Bangkok, after a second Thai soldier in the space of a week lost a limb to a landmine it said had been laid recently in the disputed area.

Thailand’s military on Thursday said Cambodia deployed a surveillance drone before sending troops with heavy weapons to an area near disputed Ta Moan Thom temple along the eastern border, around 360 km from the capital Bangkok.

Cambodian troops opened fire and two Thai soldiers were wounded, a Thai army spokesperson said, adding Cambodia had used multiple weapons, including rocket launchers.

A spokesperson for Cambodia’s defence ministry, however, said there had been an unprovoked incursion by Thai troops and Cambodian forces had responded in self-defence.

Cambodia’s influential former premier Hun Sen in a Facebook post said two Cambodian provinces had come under shelling from the Thai military.

Thailand’s acting Prime Minister Phumtham Wechayachai said the situation was delicate.

“We have to be careful,” he told reporters. “We will follow international law.”

For more than a century, Thailand and Cambodia have contested sovereignty at various undemarcated points along their 817 km (508 miles) land border, which has led to skirmishes over several years and at least a dozen deaths, including during a weeklong exchange of artillery in 2011.

Tensions were reignited in May following the killing of a Cambodian soldier during a brief exchange of gunfire, which escalated into a full-blown diplomatic crisis and now has triggered armed clashes.

An attempt by Thai premier Paetongtarn Shinawatra to resolve the recent tensions via a call with Hun Sen, the contents of which were leaked, kicked off a political storm in Thailand, leading to her suspension by a court.

Chamnan Chuenta, governor of Thailand’s Surin Province, in a Facebook post on Thursday asked residents of the district abutting the temple to shelter in their homes and prepare for evacuation.

Cambodia has many landmines left over from its civil war decades ago, numbering in the millions according to de-mining groups.

But Thailand maintains landmines have been placed at the border area recently, which Cambodia has described as baseless allegations.