North Korea has moved new firepower units into firing positions along its border with South Korea, Kim Yo Jong, the powerful sister of leader Kim Jong Un, said on Wednesday, according to North Korean state media reported by AFP and Yonhap. The deployment claim is Pyongyang's own account, carried by the state-run Korean Central News Agency (KCNA); it has not been independently verified on the ground.

KCNA reported on Wednesday that Kim Yo Jong and Pak Jong Chon, an adviser to North Korea's Ministry of National Defense, inspected key southern border fortification sites on Tuesday, along with Workers' Party secretary Ri Il Hwan. Kim said the country's military leadership had underlined the need to make clear to Seoul that its new firepower units had already taken their firing positions, the Korea JoongAng Daily reported, citing KCNA via Yonhap.

She also said Kim Jong Un had "issued an order to fortify the border with an enemy state to be eternally impregnable", according to state media, and ruled out any compromise over the border, saying North Korea would not yield in exercising what it considers its territorial sovereignty. She described the drive to fortify the southern border as irreversible.

Pak inspected the barriers being built to make the border permanent and warned that any move by South Korea — beyond warning broadcasts and warning shots — that directly threatened North Korean troops should be met with an immediate counterattack, according to KCNA as reported by the Korea JoongAng Daily. "If the enemy troops make a provocation actually threatening the safety of our service personnel... The border forces of the DPRK must take very proficient, specialized and overwhelming military action," he said, using the acronym for North Korea's official name, AFP reported. He also dismissed claims that North Korean troops had crossed the border as attempts to shift responsibility for rising tensions onto the North.

Tensions between Seoul and Pyongyang have soared since South Korea last month blamed an explosion inside the Demilitarised Zone (DMZ) separating the two countries on landmines laid by North Korea, an accusation Pyongyang has rejected, AFP reported. Kim Yo Jong said a day earlier that the South's use of loudspeaker broadcasts and warning shots had "gone beyond the red line", while threatening the deployment of more tactical strike means along the southern border.

Seoul's military on Tuesday accused Pyongyang of attempting to shift the blame for escalating tensions, while confirming the use of loudspeakers and warning shots as "legitimate defensive measures to prevent North Korean troops from crossing the MDL (Military Demarcation Line) and to drive back troops that have crossed it", AFP reported. Jin Yong-sung, chairman of South Korea's Joint Chiefs of Staff, also ordered the military to "respond with firm resolve" should North Korea use Seoul's actions as a pretext for aggressive action.

Hong Sung-pyo, a senior researcher at the Korea Institute for Military Affairs, told AFP on Wednesday that the claimed movements should be taken seriously. "Of the developments we have seen so far, this appears to be among the most serious. North Korea has conducted various demonstrations of its firepower, but this now appears to be about operational deployment," he said.

Sources: AFP; Korea JoongAng Daily / Yonhap, reporting KCNA.