The influential sister of North Korean strongman Kim Jong Un, Kim Yo Jong, attacked South Korea's Defence Minister Suh Wook for his comments on his country's offensive capabilities against North Korea.
Suh is a "senseless and scum-like guy," Kim was quoted as saying by state media on Sunday.
The senior official of the ruling Workers' Party accused Suh of making reckless remarks about a "pre-emptive strike," raising tensions on the Korean peninsula. She also threatened that South Korea risked a "serious threat" because of it. She did not elaborate.
Suh had said publicly on Friday that South Korea's armed forces had the capability to "precisely and rapidly" attack the point of origin of North Korea's missile launches as well as its command posts as soon as there were clear signs of an attack on South Korea.
Verbal attacks by North Korea against members of the South Korean government are not uncommon. Kim's statement came at a time when tensions in the region are rising again.
North Korea had recently alarmed its neighbouring countries by testing a new nuclear-capable intercontinental ballistic missile (ICBM).
UN resolutions prohibit the widely isolated country from testing missiles of any type capable of carrying a nuclear warhead. North Korea's long-range missiles are also seen as a major threat by the United States.
A separate statement by Pak Jong Chon, secretary of the Workers' Party Central Committee, said on Sunday that North Korea's army would mercilessly direct all its military power to destroy important targets in Seoul and the South Korean army if it carried out a pre-emptive strike or other dangerous actions.
