A North Korean man was caught after crossing into South Korea via the eastern border, the Joint Chiefs of Staff (JCS) said Wednesday, amid a possibility that he could have sought to defect to the South.

South Korean troops detected the man at around 4:20 a.m. through a CCTV surveillance camera as he was moving south near a military checkpoint located inside a restricted area north of the Civilian Control Line in the east coast border town of Goseong, according to the JCS.

After a three-hour manhunt, the man was taken into custody around 7:20 a.m, it added.

"The man is presumed to be a North Korean, and an investigation is under way in cooperation with related authorities into other details, such as how he ended up here and whether he has an intention to defect," JCS said in a statement.

"JCS is also checking the overall surveillance posture across the border. The North Korean military has not shown any unusual moves as of now," the statement read.

The man is known to be in his 20s and has expressed his intention to defect. But it is not immediately clear if he is a soldier or a civilian and how he was able to cross the heavily fortified border.

"An additional probe is needed to figure out details, including the possibility that he came here not across the land border but via the sea," a military official said.

The military is expected to come under fire for failing to detect the man's border crossing.

A similar security breach happened in November when a North Korean civilian crossed the border undeterred and was found, also in the town of Goseong, in a suspected defection attempt.

Malfunction of sensors installed at the fences and other loopholes were blamed at the time.

Tuesday's incident came even after the defense ministry has taken steps to improve the surveillance system.

The Civilian Control Line, which is some 5 to 20 kilometers south of the inter-Korean Military Demarcation Line, was established after the 1950-53 Korean War over security and safety concerns. (Yonhap)