The sister of North Korean leader Kim Jong Un has slammed the South's foreign minister as "impudent" for casting doubt over Pyongyang's claim that the country has no coronavirus cases, state media reported Wednesday.
Nuclear-armed Pyongyang closed its borders in January, sealing itself off from the outside world in an effort to avoid contamination, and has long insisted that it has had no cases.
Kim himself reiterated the claim at a huge military parade in October.
Experts suggest it is unlikely, given that the virus first emerged in neighbouring China, its main provider of trade and aid.
South Korean Foreign Minister Kang Kyung-wha told a forum in Bahrain on Saturday that it was "hard to believe" that the North had no coronavirus cases, adding that Pyongyang had been unresponsive to Seoul's offers to help tackle the disease.
The pandemic "in fact has made North Korea more North Korea -- ie more closed, very top-down decision-making process where there is very little debate on their measures dealing with Covid-19", Kang said.
"All signs are that the regime is very intensely focused on controlling the disease that they say they don't have."
Kim Yo Jong, sister and key adviser to the North Korean leader, condemned Kang in a statement carried by the official Korean Central News Agency on Wednesday, calling her comments "impudent" and accusing her of seeking to worsen the already strained inter-Korean relationship.
"It can be seen from the reckless remarks made by her without any consideration of the consequences that she is too eager to further chill the frozen relations between the north and south of Korea," Kim said.
"We will never forget her words and she might have to pay dearly for it."
The statement came with discussions between Pyongyang and both Washington and Seoul at a standstill following the collapse of the 2019 Hanoi summit between Kim and US President Donald Trump over what the North would be willing to give up in exchange for sanctions relief.
In June, Pyongyang blew up a liaison office with the South on its side of the border -- paid for by Seoul -- saying it had no interest in talks.
The North also has yet to comment on the election of Joe Biden as US president, nor has its state media reported the result. Biden has previously characterised Kim Jong Un as a "thug".
Kim Yo Jong's statement came with US Deputy Secretary of State Stephen Biegun, who has led denuclearisation talks with Pyongyang under the Trump administration, currently on a visit to Seoul.