As fighting spread to at least six areas along the arcane frontier, Thailand’s military closed crossings between the countries. The fighting spurred at least 40,000 civilians from more than 80 villages near the border to flee to makeshift bomb shelters of sandbags and car tires.

Thailand and Cambodia exchanged heavy artillery fire for a second day on Friday as their worst fighting in over a decade intensified and spread to new areas.

At least 16 people have been killed and tens of thousands have been displaced as fighting extended to a second day.