PUTRAJAYA, Malaysia — Thailand and Cambodia have agreed to an “immediate and unconditional” ceasefire in a significant breakthrough to resolve deadly border clashes that entered a fifth day, Malaysian Prime Minister Anwar Ibrahim said Monday.

The Southeast Asian neighbors waging their deadliest conflict in more than a decade accuse each other of starting the fighting last week.

Thai and Cambodian leaders agreed to halt hostilities in their deadliest border conflict in more than a decade, after a push by the US and regional powers for a diplomatic resolution.