The soldier suffered critical intestinal wounds as he escaped to South Korea after coming under fire attack by four North Korean soldiers.
A North Korean soldier is expected to survive critical wounds he received when his fomer comrades fired a hail of bullets at him as he made a defection dash to South Korea, the South's government and military said on Tuesday.
The soldier had on Monday sped towards the border in a "peace village" in the heavily guarded demilitarised zone, in a four-wheel drive vehicle.
But when a wheel came loose, he fled on foot as four North Korean soldiers fired about 40 rounds at him, said Suh Wook, chief director of operations at South Korea's Joint Chiefs of Staff, briefing lawmakers.
"Until this morning, we heard he had no consciousness and was unable to breathe on his own but his life can be saved," Suh said.
Surgeons had removed five bullets from the soldier's body, leaving two inside, Suh added, to murmurs from lawmakers who said the soldier's escape was "right out of a movie".
The soldier took cover behind a South Korean structure in a Joint Security Area (JSA) inside the demilitarised zone between the two Koreas.
North Korea has not said anything about the soldier.
On average more than 1,000 North Koreans defect to the South every year, most travel via China.
It is unusual for a North Korean to cross the land border dividing the two Koreas, which have been in a technical state of war since their 1950-53 conflict ended in a truce, not a peace treaty.
The UN Command, in place since the end of the war, said an investigation into the incident was being conducted.
The soldier, who was not armed, was flown in a UN Command helicopter to an operating theatre where doctors began working to save him even before he was out of a uniform that indicated he held a lower rank, Suh said.
South Korean officials have yet to identify where the soldier came from or what his intentions were.
Lee Cook-jong, the surgeon in charge of the soldier's care at the Ajou University Hospital, told reporters he was suffering from critical intestinal damage.
Monday was the first time since 2007 a North Korean soldier had defected across the JSA.
Unlikely for North to completely denuclearise in short time
South Korean President Moon Jae-in said on Tuesday it would not be easy for North Korea to completely destroy its nuclear weapons in a short time considering the state of its arsenal.
Speaking to reporters in the Philippines, Moon also said if North Korea agreed to talks, negotiations could be held with all options open although it was too early to say specifically what.
Moon's remarks were made available by his presidential office, the Blue House.