A South Korean delegation met North Korean leader Kim Jong Un on Monday, a South Korean official said, after arriving in the North on a visit aimed at encouraging North Korea and the United States to talk.
Both North Korea and the United States have expressed a willingness to talk, but the long-held US position is that the North first give up its nuclear weapons program.
The North, which has vowed never to give up its nuclear deterrent against what it sees as US hostility, says it will not sit down to talks under preconditions.
Reclusive North Korea, which has made no secret of its pursuit of a nuclear-tipped missile capable of reaching the mainland United States in defiance of UN Security Council resolutions, is also concerned about joint US-South Korea military exercises, which it sees as preparation for war.
South Korean officials have said the drills will start next month as planned, after being postponed for the Winter Olympics held last month in South Korea.
The 10-member South Korean delegation, led by National Security Office head Chung Eui-yong, was greeted by North Korean officials after landing in Pyongyang, said Kim Eui-kyeom, a spokesman for South Korea's presidential office.
The North Koreans at the airport included Ri Son Gwon, chairman of the Committee for the Peaceful Reunification of the Country, and Kim Yong Chol, who heads the United Front Department, the North Korean office responsible for handling inter-Korean affairs. Both visited South Korea last month during the Winter Olympics.
The South Korean delegation was later invited to join Kim Jong Un for dinner, the South Korean spokesman added.
The South Korean officials are the most senior officials from the South to meet Kim Jong Un since he took power in late 2011 following the death of his father, Kim Jong Il.
"We will deliver President Moon Jae-in's wish to bring about denuclearisation of the Korean peninsula and permanent peace by extending the goodwill and better inter-Korean relations created by the Pyeongchang Winter Olympics," Chung said in South Korea before the delegation's departure.
Chung's team includes National Intelligence Service chief Suh Hoon and Vice Unification Minister Chun Hae-sung.
The government hopes the visit will create "a positive atmosphere", Unification Ministry spokesman Baik Tae-hyun told a regular briefing.
Chung and Suh are due to fly to Washington later in the week to brief US officials on their discussions in the North.
Thawing relations between the Korean neighbours have prompted speculation about direct talks between Washington and Pyongyang after months of tension and exchanges of bellicose insults between US President Donald Trump and Kim Jong Un fuelled fears of war.
North Korea has not carried out any weapons tests since late November, when it tested its largest intercontinental ballistic missile. Inter-Korean talks began after Kim Jong Un said in his New Year's address that he wanted to engage the South.
North Korea later sent athletes to the Olympics, as well as a high-ranking delegation that included Kim's sister, Kim Yo Jong.
Impoverished North Korea and the rich, democratic South are technically still at war because their 1950-53 conflict ended in a truce, not a peace treaty.
The North regularly threatens to destroy the South and its main ally, the United States, which stations 28,500 troops in the South, a legacy of the Korean War.
"Neither sanctions nor provocations nor threats can ever undermine our position of a nuclear weapons state," the North's Rodong Sinmun newspaper said recently.
"Hoping that the DPRK would abandon its nuclear programmes is as foolish an act as trying to wish seas to get dried up," it said, referring to itself by its official name, the Democratic People's Republic of Korea.