North Korean leader's sister tours border fortifications and warns 'new firepower units' have taken firing positions against South Korea

Kim Yo Jong praised the frontline efforts as a 'sacred and great undertaking' in support of her brother Kim Jong Un's drive to cut all ties with Seoul permanently. Tensions have escalated after three South Korean soldiers were wounded by land mine explosions on September 21. Seoul formally attributed the mines to North Korea this month. Pyongyang has denied any involvement and issued fresh threats of retaliation.

She toured the border on Tuesday with Marshal Pak Jong Chon, a top military official.

A day earlier she threatened to restart anti-Seoul loudspeaker propaganda broadcasts.

Troops were reminded of the order to make the border 'eternally impregnable'.