Fresh fighting erupted along the Thailand-Cambodia border early Monday, raising fears of derailing ongoing diplomatic efforts to restore peace between the two neighbors. The clashes, which began on December 8, have already claimed at least 40 lives and displaced nearly one million people on both sides. ASEAN foreign ministers are meeting in Malaysia to discuss ways to revive a ceasefire originally brokered in July under U.S. mediation.

Cambodia’s Defense Ministry accused Thailand of launching four bomb attacks in Banteay Meanchey province and using toxic gas in the Preah Chan area. Thai media reported artillery exchanges in Sa Kaeo province, though Bangkok has yet to issue an official statement. Cambodian media said shelling in Battambang injured at least one civilian.

The renewed hostilities come as both governments trade blame, complicating ASEAN’s mediation efforts. Observers warn that without restraint, the conflict could destabilize regional security and disrupt cross-border trade, while humanitarian agencies struggle to assist the displaced populations.