Kim Yo-jong. Yonhap

In her first known official statement, the younger sister of North Korean leader Kim Jong Un on Tuesday leveled diatribes and insults on South Korea for protesting over her country's latest live-fire exercises.

Believed to be in her early 30s, Kim Yo Jong is in charge of propaganda affairs and has frequently appeared at her brother's major public events including summits with U.S. President Donald Trump and other regional leaders. But her statement carried by state media, the first in kind, indicated her political status has been further elevated.

In the statement, she criticized South Korea's presidential office of Blue House for expressing strong concerns over the North's firing drills and urging it to stop such an act that doesn't contribute to efforts to reduce military animosities.

''As far as I know, the South side is also fond of joint military exercises and it is preoccupied with all the disgusting acts like purchasing ultra-modern military hardware,'' Kim Yo Jong said. ''They meant they need to get militarily prepared but we should be discouraged from military exercises. Such a gangster-like assertion can never be expected from those with normal way of thinking.''

Describing the Blue House as ''a mere child'' and ''a burnt child dreading fire,'' she went on to say that ''How come can all its words and acts be so perfectly foolish in detail.''

Kim Yo Jong still didn't mention by name liberal South Korean President Moon Jae-in, whom she met several times. She only said: ''The South side's response is so regretful and disappointing but it is somewhat fortunate that it was not direct statement of the president.''

Earlier Tuesday, state media said Kim Jong Un supervised a live-fire rocket artillery exercise in an apparent reference to the two short-range ballistic missile launches reported by South Korea's military a day earlier. On Saturday, North Korea said Kim Jong Un also guided an artillery drill aimed at testing the combat readiness of military units.

The back-to-back firing exercises were an apparent show of force by Kim, who had earlier vowed to bolster his nuclear deterrent and warned of ''shocking action'' over now-stalled nuclear negotiations with Trump. The latest firing drills were his first weapons tests since late November.

Kim Yo Jong's statement was issued in her capacity as a first vice-department director of the Workers Party's Central Committee. She also serves as an alternate member of the North's powerful Politburo and a member of the rubber-stamp parliament. South Korean officials and experts say she's virtually the North's top propaganda official.

Kim Yo Jong's statement ''suggests that her status and influence have been expanded to such an extent as to express her opinions externally and beyond playing a role of assisting Chairman Kim Jong Un on his public activities,'' said analyst Cheong Seong-Chang at South Korea's private Sejong Institute.

Kim Yo Jong took a prominent role in Kim Jong Un's series of summits with Trump and Moon since North Korean entered talks on the fate of its advancing nuclear arsenal in 2018.

During one of the three summits with Moon in 2018, Kim Yo Jong handed her brother a pen when he signed the guestbook, and took his gloves after he shoveled dirt on a ceremonial tree and a bouquet of flowers that he'd been handed at the border. Her proximity to her brother during the summit sparked outside speculation that she may be the No. 2 in the North after her brother executed and purged potential rivals who could pose a threat to his family's rule.

Earlier in 2018, she came to South Korea to attend the opening ceremony of the Pyeongchang Winter Olympics, becoming the first member of the North's ruling family to visit the South since the end of the 1950-53 Korean War. At the time, she met Moon and conveyed her brother's invitation to meet in Pyongyang. (AP)