South Korea sent two helicopters to battle a wildfire inside the Korean Demilitarized Zone (DMZ), Seoul’s military said Friday, adding it had warned North Korea in advance of its firefighting mission along the heavily armed border area.

Observers claimed the Pyongyang troops might have mistakenly crossed the boundary while fortifying their side with anti-tank barriers or mines.

South Korea's military fired warning shots after North Korean soldiers crossed the rivals' tense border on Tuesday, South Korean officials said, the first known border intrusion by North Korea in nearly a year.