Seoul: North Korean leader Kim Jong Un's sister, Kim Yo Jong, inspected frontline areas where soldiers are reinforcing the heavily armed border with South Korea and renewed a threat to retaliate against any South Korean provocation targeting the fortification work, state media said Wednesday.

The visit came amid rising tensions between the war-divided rivals, with Pyongyang warning border troops to respond if South Korean forces threaten their safety. The developments follow Seoul's pledge to respond firmly to further provocations by the North.

North Korea's official Korean Central News Agency (KCNA) said Kim Yo Jong toured the border areas on Tuesday with Korean People's Army Marshal Pak Jong Chon, one of her brother's senior military officials.

Kim described the fortification efforts as a “sacred and great undertaking” supporting her brother's policy of permanently severing ties with South Korea, which he has declared his most hostile adversary.

“Our military leadership underlined the need to make those rogues aware that our new firepower units have taken their firing positions,” she said, reiterating the order to make the border with the “enemy... eternally impregnable”.

Pak accused Seoul of making “deliberate, premeditated and absurd” claims to blame Pyongyang for the tensions and threatened an “overwhelming response” to South Korean provocations. He denied that North Korean soldiers had crossed the border during fortification work, saying the North's military knew its borderline, KCNA reported.

Tensions have risen since three South Korean soldiers were injured in land mine blasts on September 21. Following an inspection with the US-led United Nations Command, Seoul formally blamed North Korea for planting the mines and urged Pyongyang to apologise and clear remaining mines. North Korea denied responsibility and warned it would retaliate if provoked.

Kim's inspection came a day after she warned that North Korea could resume anti-Seoul propaganda broadcasts using loudspeakers and deploy more powerful weapons along the border. She accused South Korea of firing warning shots and broadcasting warnings towards North Korean soldiers engaged in fortification work, allegedly on the pretext that they had crossed the border.

South Korea's Joint Chiefs of Staff chairman, Jin Yong-Sung, called her threat “intolerable” and ordered the military to “sternly respond” to potential provocations.

North Korea has been strengthening its border defences since April 2024, adding mines, barbed-wire fences, anti-tank barriers and other fortifications along the frontier. South Korea's military says North Korean soldiers have crossed the military demarcation line 50 times this year during the work, prompting Seoul to respond with warning shots and broadcasts.

The two countries remain separated by the Demilitarized Zone, established under the 1953 armistice that ended active fighting in the Korean War.

(With inputs from AP via PTI & Reuters)