WASHINGTON — The United States expressed alarm Tuesday over ongoing clashes and mounting casualties along the Cambodia–Thailand border as fighting between the two Southeast Asian nations entered a second day.

In a statement released by the State Department, U.S. Secretary of State Marco Rubio said the government is “concerned” by the violence and urged Phnom Penh and Bangkok to immediately halt military operations.

“We strongly urge the immediate cessation of hostilities, the protection of civilians, and for both sides to return to the de-escalatory measures outlined in the October 26 Kuala Lumpur Peace Accords,” Rubio said.

The renewed border confrontation has drawn international attention amid fears the fighting could escalate further if not contained.