South Korean officials said Monday that a North Korean soldier defected by crossing the heavily fortified border between the two countries.

An official from South Korea's Ministry of National Defense told the Yonhap News Agency on condition of anonymity that the soldier crossed the border near the town of Hwacheon in central Gangwon Province, northeast of Seoul. The official said the defector was under investigation, but did not give the man's name or elaborate on a motive for his crossing over.

The New York Times reported that the soldier, believed to be in his late teens, presented himself at a South Korean guard post. An official told the Associated Press that the soldier told the defense ministry that he was beaten regularly and had grievances about the North Korean regime.

Direct defections across the Korean demilitarized zone (DMZ), one of the most heavily fortified borders in the world, are extremely rare. The last North Korean soldier to defect across the DMZ did so in 2012, when he scaled three barbed-wire fences and knocked on the door of some South Korean barracks, in an incident that caused the Seoul government great embarrassment.

Many North Koreans who attempt to leave the communist country attempt to cross the border with China before attempting to arrange travel to South Korea via other Southeast Asian nations.

Yonhap had reported Sunday that North Korean soldiers were planting anti-personnel mines on their side of the DMZ in an effort to discourage their comrades from defecting. The agency reported that patrols of approximately 20 soldiers were gathering military intelligence and restoring signposts marking the DMZ.

According to the South Korean government, 1,396 North Koreans defected to the South in 2014. It is believed that more than 28,000 North Koreans have defected to the South since the onset of a disastrous famine in the late-1990s.

The Associated Press contributed to this report.

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