An unidentified person presumed to be a South Korean citizen reportedly crossed the heavily fortified inter-Korean border in the eastern region into North Korea on Saturday night.

South Korea's Joint Chiefs of Staff (JCS) said on Sunday that surveillance equipment detected the person at 9:20 p.m. inside the Military Demarcation Line in the eastern border in Gangwon Province.

The JCS said the military immediately mobilized troops to capture the person, but the defector was spotted crossing the line into the North at around 10:40 p.m.

A JCS official said that the defector was first detected by surveillance equipment at around 6:40 p.m., but a person who was monitoring the surveillance feed failed to recognize it.

The JCS said that the South Korean authorities sent a message to the North regarding the incident on Sunday morning.

It has not been confirmed whether the defector is alive.