The sister of North Korean leader Kim Jong-un on Tuesday criticized South Korean President Moon Jae-in for his speech on the North's recent missile launches, mocking him as a "parrot" that repeats the United States' "gangster-like logic."

Kim Yo-jong made the criticism in a statement after Moon said on Friday in a speech that any action that could undercut the mood for dialogue is "undesirable," hours after Pyongyang confirmed its test-firing of short-range ballistic missiles.

She said it makes no sense for Moon to criticize the North's "self-defense" missile test after he described South Korea's own missile tests as efforts to build peace and dialogue in a speech in July last year.

"He meant the test-firing of ballistic missiles conducted by the Defense Science Institute of South Korea is for peace and dialogue in the Korean peninsula but that conducted by the Academy of Defense Science of the DPRK is something undesirable that arouses serious concern among the people in the South and chills the atmosphere for dialogue," Kim said in the statement carried by the Korean Central News Agency.

DPRK stands for the North's official name, the Democratic People's Republic of Korea.

"We can hardly repress astonishment at his shamelessness," she said. "Such illogical and brazen-faced behavior of South Korea is exactly the same as the gangster-like logic of the US faulting the right of the DPRK to self-defense as a violation of the UN 'resolutions' and 'threats' to the international community.

"He can not feel sorry for being 'praised' as a parrot raised by America," she added. "This could be what is described as self-contradictory and being caught in one's own trap."

Seoul's unification ministry handling cross-border issues expressed "strong concern" and urged Pyongyang to respect each other under any circumstances in terms of acts and words.

The ministry still reaffirmed its commitment to helping jump-start stalled talks with North Korea and establish lasting peace on the Korean Peninsula.

North Korea confirmed Friday that it test-fired new tactical guided missiles a day earlier, marking its first launch of ballistic missiles in about a year and also the first of its kind since the inauguration of the Joe Biden administration.

Pyongyang has slammed South Korea and Washington for taking issue with what it sees as the exercise of its self-defense right. On Saturday, the North accused Biden of "provocation" for criticizing its recent missile launches, warning the US will face "something that is not good" if such "thoughtless remarks" continue.

Tuesday's remarks came about two weeks after Kim issued a harshly worded statement, slamming South Korea over its joint military drills with the US. She also threatened to scrap a tension-easing military deal and disband a party organ tasked with inter-Korean affairs.

She also warned the US government not to engage in hostile acts, saying, "If it wants to sleep in peace for coming four years, it had better refrain from causing a stink at its first step."

Meanwhile, the KCNA confirmed Kim's official job title by referring to her as vice-director of the Information and Publicity Department of the Central Committee of the ruling Workers' Party.

Kim was promoted to first vice-director of the department in October 2017 but has been presumed to be working at the Organization and Guidance Department tasked with organizational issues of the party since late 2019.

Regarded as one of the closest aides to leader Kim, she appears to be playing a key role in handling matters related to South Korea and the US. (Yonhap)