Half a million evacuees in Cambodia and Thailand are sheltering in pagodas, schools and other safe havens after fleeing a renewed eruption of fighting in a century-old border dispute.

At least 13 people, including Thai soldiers and Cambodian civilians, have been killed in the latest spate of fighting, now in its third day on Wednesday, officials said, while more than 500,000 have fled border regions where jets, tanks and drones are waging battle.

The Southeast Asian neighbours dispute the colonial-era demarcation of their 800-kilometre (500-mile) frontier, where competing claims to historic temples have spilled over into armed conflict.

This week’s clashes are the deadliest since five days of fighting in July, which killed dozens and displaced about 300,000 people before a shaky truce was agreed.

Both sides blame each other for instigating the renewed conflict, which on Tuesday expanded to five provinces in both Thailand and Cambodia.

On Wednesday, Cambodia withdrew from the Southeast Asian Games, hosted by Thailand, with its Olympic committee “citing serious concerns and requests from the families of our athletes for their relatives to return home immediately”.