North Korean troops had recently crossed the border and deliberately planted the three land mines that inflicted serious injuries on two South Korean soldiers, the Joint Chiefs of Staff said Monday, condemning the provocation and warning of “severe punishment.”

On Aug. 4 at around 7:40 a.m., two Army staff sergeants were critically wounded in a mine blast while patrolling the southern part of the heavily fortified demilitarized zone in Paju, Gyeonggi Province. The explosion nearly severed the right ankle of 23-year-old Kim and a larger part of both legs of 21-year-old Ha.

In retaliation, the South Korean military restarted loudspeaker propaganda broadcasts in more than 11 years, on an irregular basis in two frontline regions as of 5 p.m. Related equipment was pulled out in 2004 in line with an inter-Korean agreement and then reinstalled at 11 spots after the North’s 2010 sinking of the South’s corvette Cheonan, but had since remained idle.

“The enemy’s act this time was clearly a deliberate provocation that directly defies the truce and inter-Korean nonaggression pacts,” Defense Minister Han Min-koo told the troops during a visit to a guard post 750 meters away from the blast site.

“I will have the enemy pay a severe price of its provocations. … In case of its provocation, you must not hesitate and resolutely and firmly respond with confidence, under the command of the GP chief.” 

Following a two-day joint probe through Aug. 7 with the United Nations Command, the JCS has concluded that steel springs, firing pins and other perceived debris of the detonated devices retrieved from the scene corroborate with the wooden-box mines used by the North Korean military.

The JCS ruled out the possibility that the equipment had drifted south with the soil, such as by torrential rains, citing the lack of dirt around the mines, their buried position until the detonation and the “strong odor” of pine resin that exuded from the wreckage.

“The incident has been found to be a clear provocation in which North Korean soldiers illegally breached the Military Demarcation Line and intentionally emplaced wooden-box mines,” said Koo Hong-mo, a two-star general in charge of operations at the JCS, issuing condemnation over what he called a “nasty act that any normal military cannot even think of.”

The UNC issued a separate statement lambasting Pyongyang’s violation of the armistice agreement, calling for general-level talks with its military.

“The investigation determined that the devices were recently emplaced, and ruled out the possibility that these were legacy land mines which had drifted from their original placements due to rain or shifting soil,” the UNC said.

In a video clip of the second detonation filmed through a thermal observation device and unveiled by the JCS, a cloud of dust suddenly soared into the air, sending several soldiers flying. They were rushing to rescue Ha who was injured in the first explosion about five minutes before.

Despite the series of accidents and their colleagues’ wounds, the servicemen managed to retreat and evacuate in a calm manner.

The probe’s results mark a fresh setback in already strained cross-border ties days before the two Koreas celebrate the 70th anniversary of the peninsula’s liberation from Japanese colonial rule.

The latest border intrusion appears to be aimed at interfering in the Ulchi Freedom Guardian, an annual South Korea-U.S. military exercise expected to kick off later this month for a two-week run, another JCS official said.

“It apparently sought to interrupt the forthcoming UFG by obscuring the instigator of the provocation and creating discord inside the South,” the official told reporters on customary condition of anonymity due to the sensitivity of the matter.

Given Pyongyang’s longstanding disapproval of the loudspeaker program, tension is set to only escalate and concerns over another provocation ahead of the anniversary of the founding of its ruling Workers’ Party in October.

The blast also triggered concerns over the seemingly porous defense posture around the highly tense area given that the mines were embedded just underneath a gate to the DMZ, which is watched by the South Korean Army, 440 meters south of the demarcation line. The North Koreans are likely to have come down between July 23 and Aug. 2, said Army Brig. Gen. Ahn Young-ho, who lead the investigation.

The Kim Jong-un regime is believed to have tightened border controls to curb a constant defector outflow since he took power in December 2011. Its military has also been staging more drills for surprise attacks and ambush infiltrations into the DMZ areas, while nearly 1,300 wood or concrete markers have been set up every 200 to 300 meters along the border.

Yet the Army has been closely tracking the North’s recent mine-planting activities and thus strengthened surveillance, Ahn said, though noting that weather and other factors posed hurdles for their efforts.

“The area is easily eclipsed by the iron fence and surrounded by trees, making it difficult for us to monitor if the enemy enters north of the fence, which I believe the enemy took advantage of,” he said at a news conference.

“And as the gate area is where we always come and go by, we might have somewhat neglected detection activities, assuming that there would not be any mines there.”

More than 1 million M-14 and M-16 antipersonnel and antitank mines are expected to be scattered throughout the DMZ area.

A 2008 U.N. report said land mines kill 15,000 to 20,000 people every year.

Global efforts to stem the fatalities resulted in the 1999 Ottawa Convention, which prohibits the use, stockpiling, production and transfer of antipersonnel land mines. But the treaty has yet to be endorsed by the two Koreas, the U.S. and other countries including Russia, China and India.

According to an August 2014 report by the Human Rights Watch, only 11 countries around the world still produce the weapons or sustain the right to do so, four of them are thought to be actively churning them out ― South Korea, India, Pakistan and Myanmar. The U.S. has not produced antipersonnel mines since the late 1990s and pledged last year to destroy its stockpiles not required for the defense of the southern part of the peninsula.

By Shin Hyon-hee (heeshin@heraldcorp.com)