Story highlights The deserter crossed the border with his personal firearm in the early morning fog

He was the fourth North Korean soldier to defect to South Korea in 2017

Seoul, South Korea (CNN) A young, "low-ranking" North Korean soldier defected to South Korea across the demilitarized zone (DMZ) between the two countries early Thursday morning, South Korea said.

The soldier, aged in his late teens or early 20s, was carrying a personal firearm when he crossed the DMZ in heavy fog just after 8.00 a.m. local time, South Korean authorities said.

It is the second defection across the heavily-guarded border in less than two months; another North Korean soldier was shot multiple times while dramatically escaping to the South on November 13.

No shots were fired during the latest defection, South Korea's Joint Chiefs of Staff said. However, more than one hour later, around 9.30 a.m., South Korean soldiers fired 20 warning shots as North Korean soldiers appeared to search for the defector.

Several other gunshots were heard from the northern side of the border at 10.13 a.m. and 10.16 a.m., South Korean authorities said.