Heavy combat between Thailand and Cambodia has entered a second week, with Cambodia claiming Thai bombing is hitting deeper into its territory.

Thailand's military said on Monday that it has stopped fuel shipments passing through a border checkpoint with Laos because of fears they were being diverted to Cambodia, with which it is fighting a fierce border conflict.

The move came as China’s government urged both nations to exercise “utmost restraint” and de-escalate tensions.

Thailand launched air strikes against Cambodia on Monday as a new wave of fighting erupted between the southeast Asian neighbors, marking the potential collapse of a peace plan presided over by US President Donald Trump just two months ago.

Thailand said it’s taking steps to restrict exports of fuel and arms through a checkpoint with Laos on fears the goods are being diverted to Cambodia as the border clash between the two countries intensifies.

President Trump helped end a simmering conflict between Cambodia and Thailand in the summer, but the ceasefire didn't last long.

The two sides are battling over longstanding competing claims to patches of frontier land, some of which contain centuries-old temple ruins.

Thailand will hold a general election on Feb. 8, with pre-poll surveys signaling a fractured mandate as outgoing Prime Minister Anutin Charnvirakul bets that the intensifying armed conflict with Cambodia will bolster support for his conservative party.

The U.S. Embassy & Consulate in Thailand published a security alert last week following a "significant escalation" across the border region along with reports of artillery and small arms fire exchanges.