South Korea's Unification Minister, its point man for relations with the North, stepped down on Friday over heightened tensions on the peninsula, days after Pyongyang blew up its liaison office with the South.

President Moon Jae-in "accepted Unification Minister Kim Yeon-chul's offer to resign", the presidential Blue House said in a statement, after warning it will "no longer tolerate" the North's unreasonable behaviour in an unusually stern criticism earlier this week.

Kim had offered to leave on Wednesday, a day after the North demolished the liaison office, saying he "takes responsibility" for the worsening of inter-Korean relations.

The North's official KCNA news agency again blamed the South for the rising tensions on Friday, calling Seoul's condemnation of its blowing up of the office "a guilty party filing the suit first".

"All measures taken by us are punishments" that the South "deserves for their crimes", KCNA said in the commentary.

In his resignation statement, Kim expressed hope that his departure "will be a chance to pause for a bit".

"One can never overcome hatred with hatred," he told reporters, adding: "There are many wounds to heal in inter-Korean relations... We have to stop here."

Since early June, North Korea has issued a series of vitriolic condemnations of the South over anti-Pyongyang leaflets, which defectors send regularly, usually attached to balloons or floated in bottles.

Analysts say the North may be seeking to manufacture a crisis to increase pressure on the South to extract concessions.

On Tuesday it reduced the building on its side of the border that symbolised inter-Korean rapprochement to rubble, and the following day threatened to bolster its military presence in and around the Demilitarized Zone.

A South Korean guard post in the border city of Paju. Analysts say the North may be seeking to manufacture a crisis to increase pressure on the South to extract concessions
A South Korean guard post in the border city of Paju. Analysts say the North may be seeking to manufacture a crisis to increase pressure on the South to extract concessions AFP / Jung Yeon-je

Inter-Korean relations have been in deep freeze for months, following the collapse of a summit in Hanoi between North Korean leader Kim Jong Un and US President Donald Trump.

That meeting foundered on what the nuclear-armed North would be willing to give up in exchange for a loosening of sanctions.

A pro-engagement academic and a longtime confidant of Moon, Kim was appointed to the post in March last year, days after the Hanoi meeting.

Reports say John Bolton, the former US national security advisor, criticised Moon in his new memoir for encouraging both Kim and Trump to have unrealistic expectations of the other.

Moon, who has also long backed engagement with the North, has been called unrealistic by his critics for his dovish approach.

On Monday the left-leaning president gave a speech calling for inter-Korean dialogue and stressing the importance of peace on the peninsula.

But Kim Yo Jong, the powerful sister of the North Korean leader, called the speech "disgusting" and "shameless and impudent", adding Moon "seems to be insane though he appears to be normal outwardly".

Seoul retorted with unusually stern criticism, calling her remarks "senseless" and "very rude", adding it will "no longer tolerate" Pyongyang's "unreasonable acts and words".

The two Koreas remain technically at war after hostilities in the Korean War ended with an armistice in 1953 but not a peace treaty.

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