SEOUL (REUTERS)- A North Korean soldier shot while defecting to the South has undergone several surgical procedures and is in a critical condition, South Korea's government and military said on Tuesday (Nov 14), with doctors expecting to save him.

"Until this morning, we heard he had no consciousness and was unable to breathe on his own but his life can be saved," said Suh Wook, chief director of operations at South Korea's Joint Chiefs of Staff, who was briefing lawmakers regarding Monday's event.

Five bullets had been extracted from the soldier's body so far, leaving an estimated two inside, Suh added.

Lee Cook Jong, the surgeon in charge of the soldier's treatment, told reporters earlier on Tuesday his condition was critical due to intestinal damage caused by the bullets.

The soldier had sped towards the border in a vehicle when a wheel came loose, forcing him to escape on foot under fire from four North Korean soldiers who shot around 40 rounds at him, Suh said.

North Korea's military took action when the defector was spotted in the four wheel drive heading towards the border alone, Roh Jae Cheon, a spokesman for the South's Joint Chiefs of Staff, said in a media briefing on Tuesday.

The soldier took cover behind a South Korean structure within the Joint Security Area (JSA) inside the demilitarised zone between the two Koreas and was later rescued by South Korean and US soldiers at the border, the United Nations Command (UNC) said in a separate statement.

It said the soldier had been shot by several North Korean soldiers.

He was found unarmed and taken to surgery while still in his uniform, which indicated he held a lower rank, Suh said. South Korean officials have yet to identify exactly where the soldier came from and what his intentions were.

The military armistice commission of the United Nations said in the same UNC statement it had informed the North Korean military that the soldier, who was found about 50 metres south of the Military Demarcation Line, was undergoing surgery for his gunshot wounds.

Suh also said the South had later informed the North on Monday of the soldier and his ongoing treatment via loudspeakers installed at the border.

The United Nations Command said an investigation into Monday's event was ongoing.

It was the first time since 2007 a North Korean soldier had defected across the JSA. South Korean Defence Minister Song Young Moo, who was also at Parliament said it was the first time North Korean soldiers had fired towards the South's side of the JSA, prompting complaints from some lawmakers the South's military should have also fired shots towards the North.

Moon Sang Gyun, the South's defence ministry spokesman said military operations at the JSA are usually carried out under the order of the United Nations Command, which is in turn under order from the US military.

Roh said no South Korean or US soldiers were wounded during the incident and the defence ministry official said North Korea's military had not shown any unusual movements on Tuesday.