SEOUL, South Korea – Four North Korean soldiers fired about 40 rounds at a comrade fleeing into South Korea and hit him five times in the first shooting at the jointly controlled area of the heavily fortified border in more than 30 years, the South’s military said Tuesday.

South Korean soldiers did not fire their weapons, but Monday’s incident occurred at a time of high animosity over North Korea’s nuclear program. The North has expressed intense anger over past high-profile defections.

North Korean military guard outpost with its flag, left, is seen from Paju, South Korea, Tuesday, Nov. 14, 2017.

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The soldier is being treated at a South Korean hospital after a five-hour operation for the gunshot wounds he suffered during his escape across the Joint Security Area. His personal details and motive for defection are unknown and his exact medical condition is unclear.

South Korea’s military said he suffered injuries in his internal organs but wasn’t in a life-threatening condition. But the Ajou University Medical Center near Seoul said the soldier was relying on a breathing machine after the surgery removed the bullets. Lee Guk-jong, a doctor who leads Ajou’s medical team for the soldier, described his patient’s condition as “very dangerous” and said the next 10 days might determine whether he recovers.