New Delhi, Dec. 8 -- Thailand has conducted air strikes along a contested stretch of its frontier with Cambodia, the Thai army announced on Monday, marking the most serious escalation since the two neighbours agreed to a ceasefire earlier this year.

The flare-up threatens to undermine months of diplomatic effort, including a high-profile agreement brokered by US President Donald Trump and Malaysian Prime Minister Anwar Ibrahim.

Thai army spokesman Major General Winthai Suvaree said the strikes followed what Bangkok characterised as repeated Cambodian violations of the ceasefire in recent days.

"Both countries accused the other of breaching a ceasefire agreement," he confirmed, noting that Thai aircraft were deployed in response to what...