Story highlights Soldier crossed the heavily fortified DMZ last week

North Korea seeks to fortify zone after 3 soldiers defect this year

(CNN) North Korea has replaced nearly all the soldiers along the border where one of their former comrades defected, a South Korean lawmaker said Friday.

"North Korea replaced almost all of its troops, if not all, at the Joint Security Area for their failure to prevent the defection," said Kim Young-woo, chairman of the National Assembly's defense committee. "It was obviously a part of punishment for failing their mission to deter the North Korean soldier's escape. North Korea has always punished those responsible for similar failures."

Earlier, both the South Korean military and US forces in Korea told CNN they could not confirm Kim's statement. The status of the soldiers is unclear.

The change comes as the North Korean People's Army sought to prevent other soldiers from defecting by planting trees and apparently digging a trench at a section of the demilitarized zone, according to the chargé d'affaires at the US Embassy in Seoul.

Marc Knapper, the highest-ranking official at the US Embassy, tweeted a photo this week showing North Korean soldiers supervising what appears to be the planting of two trees and the digging of a trench where the North Korean soldier dashed across the border November 13.

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