The leaders of North and South Korea have exchanged letters expressing hope for improved bilateral relations, which had plummeted in the past three years amid a freeze in nuclear negotiations and the North’s accelerating weapons development.

North Korea’s state media said leader Kim Jong Un had received a personal letter from outgoing South Korean President Moon Jae-in, and replied on Thursday with his own letter appreciating Mr Moon’s peace efforts during his term in office.

Pyongyang’s official Korean Central News Agency (KCNA) said the exchange of letters showed the two leaders’ “deep trust”.

Experts say North Korea’s announcement of the letters, which came as Mr Kim possibly prepares for a nuclear test and other major provocations, is aimed at dividing public opinion in South Korea and discouraging Seoul’s new government from taking a hard line toward Pyongyang after its inauguration in May.

KCNA said Mr Moon told Mr Kim he would continue to campaign for Korean reunification even after he leaves office next month, basing his efforts on their joint declarations for peace issued after their summit meetings in 2018.

Mr Kim and Mr Moon shared views that “inter-Korean relations would improve and develop as desired and anticipated by the (Korean) nation if the (North and the South) make tireless efforts with hope,” KCNA said.

Mr Moon’s office confirmed the exchange of letters shortly after KCNA’s report, but spent hours before releasing its version of what was said, which indicated that the North did not coordinate with Seoul before announcing the exchange.

KCNA’s report was not published on the North’s official Rodong Sinmun newspaper, which is read by its domestic audience, showing that the message was intended for the South.

According to Seoul, Mr Moon in his letter to Mr Kim acknowledged setbacks in inter-Korean relations but insisted that their aspirational vows for peace during their summits in 2018 and an accompanying military agreement aimed at defusing border area clashes remain relevant as a foundation for future cooperation.

Mr Moon also expressed hope for a resumption of nuclear talks between Washington and Pyongyang and for Mr Kim to pursue cooperation with Seoul’s next government led by conservative president-elect Yoon Suk Yeol, Mr Moon’s spokesperson Park Kyung-mee said.

While sending a letter to the North’s leader is a courtesy as the South’s leaves office, analyst Cheong Seong-Chang at the South’s private Sejong Institute said, the North publicised the personal exchange with an aim to create division in South Korea ahead of a government change.

“Considering indications that North Korea is preparing for its seventh nuclear test, it’s questionable whether it was appropriate for President Moon to send a letter to Chairman Kim to express his warm greetings,” Mr Cheong said.

Mr Yoon, who takes office on May 10, has described Mr Moon’s foreign policy as being “subservient” toward North Korea, and said he would not pursue “talks for talks’ sake”.

He has vowed to strengthen South Korea’s defences in conjunction with its alliance with the United States, which he says would include enhancing pre-emptive strike capabilities and anti-missile systems to deter North Korean attacks.

Tensions on the Korean Peninsula have risen since a series of North Korean weapons tests this year, including its first flight-test of an intercontinental ballistic missile since 2017 in March, reviving the nuclear brinkmanship aimed at forcing the US to accept it as a nuclear power and to remove crippling sanctions.