Two South Korean conscripts died in apparent suicides on Sunday, the military says, weeks after another soldier shot five members of his unit.
The two men, both privates, were found hanged in separate barracks.
Both had been placed on a watch list for monitoring due to concerns over their state of mind.
South Korea operates a conscription system under which all men must serve about two years. The nation remains technically at war with North Korea.
The demilitarised zone (DMZ) which divides the two Koreas is one of the most heavily guarded areas in the world.
South Korea's conscription period is one of the longer globally, with most conscripts aged in their early 20s.
Bullying and mental health problems have been blamed for a number of previous incidents.
In June a soldier shot himself, but survived, after killing five members of his unit.
He was described as having had difficulties adjusting to military life, and had also been placed on a watch list.
Both he and one of the men who killed himself this week were assigned to the same front-line unit near the DMZ.
A defence ministry official said few measures existed to help vulnerable soldiers adapt to military life.
"We are struggling to find fundamental solutions amid the harsh reality of a lack of systematic measures to support the servicepersons and a reduction in the number of potential draftees due to the country's low birth rate," Yonhap news agency quoted the unnamed official as saying.