SEOUL: A suspected North Korean defector crossed the de facto western maritime border last month and is now in the South, Seoul’s military said Friday, days after Pyongyang said it would seal off the countries’ shared border.

The North’s army said this week it would “permanently shut off and block the southern border” by “completely cutting off roads and railways” connected to the South and building “strong defence structures”.

Seoul’s Joint Chiefs of Staff chairman Kim Myung-soo, told lawmakers on Thursday that the North’s latest moves could be “intended to prevent the external leakage of internal personnel” into the South.

“Our military secured a person suspected to be from North Korea in the West Sea in mid-September and handed him over to the relevant authorities,” Seoul’s military told AFP.

“There have been no unusual movements from the North Korean military, and we cannot confirm any further details.”

South Korea’s Yonhap news agency said that the incident involved a North Korean escaping aboard a wooden boat.

The latest case follows two recent defections: one across the heavily fortified inter-Korean land border and the other through the neutral zone of the Han River estuary, both reported by Seoul in August.

South Korea said in July that Pyongyang had planted tens of thousands of new landmines and built barriers in the border area, resulting in “multiple casualties” among the North’s soldiers when mines exploded.

Tens of thousands of North Koreans have fled to the South since the peninsula was divided by war in the 1950s.

Most defectors go overland to neighbouring China first, then enter a third country such as Thailand before finally making it to South Korea.

The number of successful escapes dropped significantly from 2020 after the North tightened its borders to prevent the spread of Covid-19, purportedly with shoot-on-sight orders along the land frontier with China.

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But the number of defectors making it to the South almost tripled last year to 196, Seoul said in January, with more elite diplomats and students seeking to escape.

Experts say defectors have likely been impacted by harsh living conditions, including food shortages and inadequate responses to natural disasters while living in the isolated North.