Kim Yo-jong will be exercising de facto control over national and global matters, several media outlets reported.
In the recent past, Jong Un has been seen taking a leading role in a new, more hard-line pressure campaign against South Korea, highlighting what analysts say is a substantive policy role that goes beyond being her brother's assistant. The 36-year-old reportedly underwent a "botched" heart operation that left him gravely ill.
"I assess him to be in a coma, but his life has not ended", he said to the media in a translated statement.
Fuelling rumours of the about the failing health condition of North Korean leader Kim Jong-un, a former aide to South Korea's late president Kim Dae-Jung, Chang Song-min has claimed that Kim is in a coma and that's why his sister Kim Yo-jong has been given powers.
"A complete succession structure has not been formed, so Kim Yo-jong is being brought to the fore as the vacuum can not be maintained for a prolonged period", he said, according to The Mirror.
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Ms Yo-jong is now chiefly involved in shaping policies toward the USA and South Korea.
South Korea's National Intelligence Service (NIS) has concluded that the move to transfer some of the powers to Kim Yo Jong establishes the fact that she has attained the position of "de-facto second in command" in the regime.
Roy Calley, a journalist who claims to have a network of contacts in Pyongyang suggests that it could be just a matter of time before an official announcement regarding Kim Jong-un's death will be made.
Kim Jong Un's reported deteriorating health has been making headlines for the past few months.
He also said the country was facing a dual challenge of fending off COVID and repairing damage from torrential rain that lashed the country in recent weeks, destroying thousands of homes and almost 100,000 acres of crops. She previously served as one of North Korea's top propagandists and is now an alternate to the Politburo - the senior body of North Korea's ruling party.