"We are deeply concerned over the current developments (and) hope both sides can properly resolve issues through dialogue and consultations," foreign ministry spokesman Guo Jiakun said.

"Good-neighbourliness and properly handling differences are in line with the fundamental and long-term interests of both sides," he said.

The neighbours are locked in a bitter spat over an area known as the Emerald Triangle, where the borders of both countries and Laos meet, and which is home to several ancient temples.

The squabble has dragged on for decades, flaring into bloody military clashes more than 15 years ago and again in May, when a Cambodian soldier was killed in a firefight.

The conflict blazed up on Thursday, with Cambodia firing rockets and artillery shells into Thailand and the Thai military scrambling F-16 jets to carry out air strikes.

At least one civilian has been killed and three others wounded.

Cambodia has long been a staunch ally of China, receiving billions of dollars in investments.

Guo said Thursday that China would adopt a "fair and impartial position" in the clashes, however.

Beijing "has and will continue to in its own way do its best to promote peace and dialogue, and play a constructive role in promoting the easing and cooling down of the situation," Guo added.