The parents of a runaway South Korean soldier holed up in a forest after allegedly killing five comrades near the North Korean border pleaded with him to surrender Monday as the military tightened a cordon meant to capture him alive.

There has been a massive manhunt for the soldier, identified only by his surname Yim, since authorities said he killed five and wounded seven Saturday night before fleeing his frontline army unit with his standard issue K2 assault rifle.

The 22-year-old also fired Sunday on the troops chasing him, injuring a platoon leader. On Monday, officials said a South Korean soldier was wounded by suspected friendly fire.

South Korean army soldiers head to search for a South Korean conscript soldier suspected of killing five comrades in Goseong. (Ahn Young-joon/The Associated Press) Troops surrounded Yim so closely Monday in the forest about 7 kilometres from the border outpost that they could toss him a mobile phone to talk to his father. Yim, who still refused to surrender, had ammunition and officials feared hemight "commit an extreme act" — an apparent reference to suicide — Defence Ministry spokesman Kim Min-seok said at a briefing.

Besides the mobile phone, Yim's parents also used a loudspeaker to try to persuade him to surrender, according to the Defence Ministry.

It wasn't clear what triggered the rampage, and there was no indication that South Korea's bitter rival, North Korea, was involved.

Reassigned to front line duty

Yim was scheduled to complete his nearly two years of mandatory military service in September, according to defence officials. Initial personality tests in April of last year put Yim within a group of soldiers who need special attention and are unfit for front line duty, a Defence Ministry official said, speaking on condition of anonymity because of department rules.

But tests last November concluded he had improved and could serve in the front line area, said the official.

The rampage comes as South Koreans grapple with worries over public safety in the wake of an April ferry disaster that left more than 300 people dead or missing.

Some in Seoul have raised questions about the discipline and readiness of South Korea's military, which is under near-constant threat from a North Korea that has recently staged a series of missile and artillery drills, traded fire with the South near a disputed maritime border and threatened South Korea's leader.

"Due to a shortage of troops, even some soldiers on the list of special attention had to be on border guard, which requires soldiers to be heavily armed. Needless to say, the military needs to come up with remedial measures to this problem," the Korea Times, said in an editorial Monday.

Mandatory conscription

Hundreds of thousands of troops from the rival Koreas are squared off along the world's most heavily armed border. The Korean Peninsula is still technically in a state of war as the 1950-53 Korean War ended with an armistice, not a peace treaty.

South Korean troops and police surrounded Yim in a forested area about seven kilometres from where the shootings occurred. Yim's parents were called in to attempt to convince him to surrender. (Ahn Young-joon/The Associated Press)

Shooting rampages against fellow soldiers happen occasionally. South Korea's military maintains a conscription system requiring all able-bodied men to serve about two years because of the North Korean threat.

In 2011, a 19-year-old marine corporal went on a shooting rampage at a Gwanghwa Island base, just south of the maritime border with North Korea. Military investigators later said that corporal was angry about being shunned and slighted and showed signs of mental illness before the shooting.

In 2005, a soldier tossed a hand grenade and opened fire at a front-line army unit in a rampage that killed eight colleagues and injured several others. Pfc. Kim Dong-min told investigators he was enraged at superiors who verbally abused him.