A person who crossed the border from South Korea into North Korea on New Year's Day was likely a defector who had slipped through the same heavily fortified frontier in the other direction to settle in South Korea in late 2020, the military said on Monday.

South Korean surveillance equipment detected an unidentified person moving into North Korean territory across the eastern portion of the border on Saturday.

The military said a security camera showed a person earlier on Saturday crawling over a barbed-wire fence along the southern edge of the border.

On Monday, the Defence Ministry said in a statement it suspects an earlier North Korean defector was the border crosser and that it is trying to confirm related information.

A ministry official said the statement refers to a former North Korean citizen who was captured south of the border in November 2020.

The man identified himself as a former gymnast and told investigators that he had crawled over barbed wire fences to defect before being found by South Korean troops, the official said, requesting anonymity citing department rules.

The official said the appearance of the person detected by the South Korean security camera on Saturday matched the former defector.

The person's fate is not known.

South Korea asked North Korea to ensure the person's safety via a military hotline communication channel.

North Korea replied that it received the South Korean messages but did not elaborate on the border crosser, according to the South Korean Defence Ministry.

About 34,000 North Koreans have fled to South Korea for economic and political reasons since the late 1990s, and only about 30 have returned home in the past 10 years, according to South Korean government records.

Defecting via the border is rare. Unlike its official name, the Demilitarised Zone, the 155-mile-long, 2.5-mile-wide border is guarded by land mines, tank traps and combat troops on both sides as well as barbed wire fences.

A vast majority of the North Korean defectors in South Korea came via China and Southeast Asian countries.