SEOUL (AFP) - South Korea's military confirmed on Tuesday the apparent suicides of two army privates, raising fresh questions over the deployment of young conscripts in frontline units after a deadly shooting spree last month.

The two privates, identified by their surnames Shin and Park, were both found hanged in their barracks on Sunday in separate locations near the heavily militarised border with North Korea, an army spokesman said.

Both men, who were in their early 20s, had been placed on a list of soldiers requiring special monitoring due to concerns over their mental stability.

The army spokesman said an investigation was under way in both cases.

The suicides followed an incident on June 21 in which a 22-year-old sergeant surnamed Lim opened fire on members of his own unit at a border guard post, killing five and wounding seven.

Lim later told interrogators that he had snapped because he felt humiliated by the other soldiers, who mocked him and drew cartoons depicting him as SpongeBob SquarePants.

Lim had also been listed as a soldier requiring special observation, and belonged to the same 22nd Infantry Division as Shin.

The South Korean armed forces rely heavily on a compulsory military service system, with conscripts - most in their early 20s - accounting for the lion's share of its 690,000 active personnel.

Experts say the pressures facing the young servicemen can be daunting when, after what is often quite a cosseted childhood and teenaged youth, they are suddenly plunged into a world of harsh military discipline.

Barrack-room bullying of fresh conscripts used to be rampant, and has been blamed for a number of suicides and shooting sprees in the past.

Tensions on the North-South Korean border have been running high in recent months, with North Korea conducting a series of ballistic missile tests.

"It's been going on for some time now, and soldiers have been under enormous pressure," Secretary-General Lee Il-Woo of the private Korea Defence Network told AFP.

"In the so-called hand-it-down phenomenon, a soldier pecked by his stressed-out superior tends to take it out on his own underling and this continues down to the lowest rung of the ladder, especially at a time of high alert."

South Korea's low birth rate has cut the number of conscripts, and there are concerns that the army, in an effort to keep up numbers along the border, has been deploying soldiers who are not mentally suited to the pressures of frontline duty.