SEOUL-- The sister of North Korean leader Kim Jong-un on Wednesday accused South Korean President Moon Jae-in of being "stupid" and warned of a "total deadlock" of inter-Korean relations for branding Pyongyang's weapons tests a "provocation."

The statement from Kim Yo-jong came shortly after Moon said that South Korea's upgrading of its missile capabilities can help deter North Korean provocation following the successful underwater test-launch of an indigenous SLBM at a local test site.

"If the slip of tongue reportedly made by the 'president' is true, it is too stupid one to be fit for the 'president of a state'... We express very great regret over his thoughtless utterance of the word 'provocation' which might be fitting for hack journalists," Kim said.

"If even the 'president' supports the act of faulting and hurting the dialogue partner, it will naturally result in a corresponding action and then the North-South relations will end up in a total deadlock," she said in the statement carried by the official Korean Central News Agency.

Kim, however, left room for change in inter-Korean ties, saying that is not what the North hopes for.

"Every word and act must be made with deep thought," she said.

Earlier in the day, North Korea fired two short-range ballistic missiles into the East Sea, just days after successfully test-firing a newly developed long-range cruise missile.

Kim blasted Moon for calling the launches a "provocation," saying they were "normal and self-defensive action."

"We are not aiming to make 'provocation' against somebody at a certain time as presumed by South Korea. What we did is part of normal and self-defensive action to carry out the key task for the first year of the five-year plan for the development of defence science and weapon system in order to implement the decisions made at our Party Congress," she said.

Source: Yonhap News Agency