The delegation, representing the South's President Moon Jae-in, is pushing for talks between the nuclear-armed regime and the United States, after Kim sent his sister Kim Yo Jong to the Winter Games in the South.

"Chairman Kim Jong Un is currently hosting a dinner for the special envoys," Moon's spokesman told a press briefing Monday evening, Yonhap news agency reported.

Kim Yo Jong's trip was the first visit to the South by a member of the North's ruling dynasty since the end of the 1950-53 Korean War, and her appearance at the Games' opening ceremony -- where athletes from the two Koreas marched together -- made global headlines.

Moon has sought to use the Pyeongchang Games to open dialogue between Washington and Pyongyang in hopes of easing a nuclear standoff that has heightened fears over global security.

In Seoul, Kim Yo Jong invited him to a summit in Pyongyang on her brother's behalf. But Moon did not immediately accept, saying the right conditions were necessary first.

Before leaving for Pyongyang, the South's national security advisor Chung Eui-yong said: "We plan to hold in-depth discussions for ways to continue not only inter-Korean talks but dialogue between North Korea and the international community including the United States."

It is a challenging task -- in defiance of UN sanctions, the isolated and impoverished North last year staged its most powerful nuclear test and test-fired several missiles, some of them capable of reaching the US mainland.

US President Donald Trump dubbed Kim "Little Rocket Man" and boasted about the size of his own nuclear button, while the North Korean leader called Trump a "mentally deranged US dotard".

They traded threats of war and sent tensions soaring before a thaw in the run-up to the Winter Olympics.

"We will deliver President Moon's firm resolution to denuclearise the Korean peninsula and to create sincere and lasting peace," delegation leader Chung told reporters.

Chung is one of five senior officials who flew to Pyongyang on Monday.

It was the first ministerial-level South Korean visit to the North since December 2007, when Seoul's then-intelligence chief travelled to Pyongyang.

Conservative Lee Myung-bak was elected the South's president the following day and took a markedly harder line on relations with the North.

- Washington connection -

Monday's delegation included spy chief Suh Hoon, who is a veteran in dealings with the North. He is known to have been deeply involved in negotiations to arrange two previous inter-Korean summits in 2000 and 2007.

The North's official Korean Central News Agency also announced their impending visit in a one-paragraph dispatch.

The 10-member group -- five top delegates and five supporting officials -- will return to Seoul on Tuesday.

Other members include Suh's deputy at the National Intelligence Service as well as Chun Hae-sung, the vice minister in Seoul's unification ministry which handles cross-border affairs.

The delegation will fly to the US on Wednesday to explain the result of the two-day trip to officials in Washington, according to the South's presidential office.

Moon, who advocates dialogue with the North's nuclear-armed regime, said last week that Washington needs to "lower the threshold for talks" with Pyongyang.

But the US has ruled out any possibility of talks before the North takes steps towards denuclearisation, and imposed what Trump hailed as the "toughest ever" sanctions on Kim's regime late last month.