North Korean Leader Kim Jong Un's sister rejected on Friday Seoul's offer of economic assistance in return for denuclearisation steps.

The declaration comes after South Korean President Yoon Suk-yeol this week proposed an "audacious" and "foolish" aid proposal that would include food, energy, and infrastructure assistance in exchange for the North's nuclear weapons development being abandoned.

Analysts had predicted that Pyongyang would reject such a deal because the North, which invests a "large portion of its GDP in weapons programs," has long stated that it will not make such a swap.

Yo Jong, Kim Jong Un's sister, termed Yoon's offer the "height of absurdity," adding that the basic premise that the North would willingly put its nuclear program on the table was incorrect.

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"To think that the plan to barter 'economic cooperation' for our honor, (our) nukes, is the great dream, hope and plan of Yoon, we came to realize that he is really simple and still childish," she said in a statement carried by the official Korea Central News Agency.

"We make it clear that we will not sit face to face with him," she added, saying "no one barters its destiny for corn cake."

“It would have been more favourable for his image to shut his mouth,” Kim Yo Jong said in her statement, addressing South Korea's President. 

She also accused the South of recycling proposals that the North had previously rejected and compared Yoon to a "barking dog".

South Korea's presidential office expressed "strong regret" at Yo Jong's "rude" words but noted that the offer of economic aid was still on the table.

"North Korea's attitude is in no way helpful to the peace and prosperity of the Korean peninsula, as well as its own future, and only promotes isolation from the international community," it said in a statement. 

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DPRK fires 2 cruise missiles towards Yellow Sea: Seoul

Earlier this week, amid tensions over the US meddling in East Asia, North Korea launched two cruise missiles from the west coast town of Onchon into the Yellow Sea, according to Seoul's Defense Ministry.

"The US and South Korean military authorities are analyzing detailed specifications such as flight distance," a Ministry official said as quoted by AFP.

It is worth noting that North Korea has not tested a cruise missile since January, as per Yonhap News Agency.