South Korea's Defense Ministry on Friday condemned North Korean leader Kim Jong-un and his sister Kim Yo-jong's criticism of President Yoon Suk Yeol and the Armed Forces Day celebration in South Korea, calling it "behavior that can never be tolerated."

North Korean state media earlier in the day reported Kim Jong-un denounced and dismissed Yoon's Armed Forces Day speech, which warned of the regime's end if it attempts to use nuclear weapons, launching a direct and vulgar verbal assault on Yoon.

This was followed by a press statement from Kim Yo-jong on Thursday evening that condemned both the Armed Forces Day celebration and Yoon's remarks.

In response, the Defense Minsitry underscored again that "North Korea will gain nothing from developing nuclear missiles, and any nuclear provocation will immediately lead to the end of the North Korean regime."

The ministry also clarified the rationale behind the specific criticisms directed at South Korea's weapon systems and strategic command during this year's Armed Forces Day event, noting that this marks a departure from past behavior.

"(This response) is directly linked to the North Korean leadership’s anxiety and unease regarding our military's robust capabilities and steadfast posture," the Defense Ministry stated.

"Furthermore, as a regime that has thoroughly deceived its citizens, North Korea is fearful that its residents will witness the impressive display of our military, which has been prominently featured in global media, leading to their paranoia and compulsion," it added.

Kim Jong-un's criticism came during his Wednesday inspection of a special operations training base in the western region, just a day after South Korea marked its Armed Forces Day with a showcase of advanced weaponry.

Kim specifically denounced Yoon's warning that North Korea would face a "resolute and overwhelming response from our military and the Korea-US alliance" if it used nuclear weapons, with Yoon adding, "That day will be the end of the North Korean regime."

"‘If’ the enemy, seized with extreme foolishness and recklessness, attempts to use armed forces encroaching upon the sovereignty of the DPRK, full of excessive ‘confidence’ in the ROK-US alliance in disregard of our repeated warnings, the DPRK would use without hesitation all the offensive forces it has possessed, including nuclear weapons," an English-language report from the state-run Korean Central News Agency quoted Kim as saying.

The ROK and the DPRK refer to the official names of South and North Korea, respectively: the Republic of Korea and the Democratic People's Republic of Korea.

Kim also insulted Yoon, calling him an "abnormal man" and a "puppet."

This marked the first time in over two years that Kim has directly criticized Yoon by name, the last instance being in his speech on North Korea's "Day of Victory" in July 2022.

Kim Yo-jong, also issued a press statement on Thursday evening denouncing South Korea's display of the Hyunmoo-5 missile and the flyover of a US strategic bomber during the Armed Forces Day event, as well as South Korea's launch of a Strategic Command on the same day.

"Though the head of our state put a precondition of the word 'if,' he re-clarified the stand to use all the offensive forces of the country without hesitation if the ROK attempts a military confrontation with the DPRK, being overconfident of the ROK-US alliance," Kim Yo-jong said in her press statement.

Kim Yo-jong also denounced Yoon’s speech, directly mentioning his name several times.

"The confrontation outcry, raised by Yoon Suk Yeol with war fever this time, is no more than a last-ditch scream of a guy at death's door," she added.

Hong Min, a senior research fellow at the government-funded Korea Institute for National Unification, pointed to the rationale behind the consecutive statements from Kim Jong-un and his sister.

"The leader and his closest confidant personally delivered these messages, underscoring the gravity of their words and the regime's intent to create a psychological barrier against the impact of South Korea’s Oct. 1 Armed Forces Day event," Hong said.

"There is a possibility that North Korea feared the inflow of information about South Korea's Armed Forces Day could cause unrest among its citizens or distort perceptions, especially regarding the notion that South Korean and US military assets might be stronger than North Korea's own weapons."

Hong pointed out, "Both Kim Jong-un and Kim Yo-jong expressed a shared concern that South Korea, overly confident in the Korea-US alliance, might attempt to infringe upon North Korea's sovereignty -- whether by violating its territory, waters, or airspace -- or seek military confrontation."

"The statements were likely intended as preemptive warnings to deter South Korea from encroaching on North Korean territory or resorting to military action during periods of heightened territorial tension following the Oct. 7 constitutional amendment," Hong said.

The Unification Ministry on Wednesday projected that North Korea would further solidify its hostile stance toward inter-Korean relations by enshrining it in constitutional amendments at the upcoming parliamentary session on Monday, potentially including new clauses defining the North Korean territory.