Korea experts say the pair are considered accessories to the 2017 assassination and could be marked for elimination as per North Korea's modus operandi.
South Korea's military begins monitoring N.Korea after satellite images of a missile launch in Pyongyang cause an international alarm.
Kim Yeon-chul's appointment comes days after the US and N.Korea held a second summit in Hanoi, but failed to reach an agreement on the denuclearisation of the Korean peninsula.
President Moon Jae-in says that he is ready to undertake anything from reconnecting rail and road links between the two Koreas to other inter-Korean economic cooperation.
Jo Song-gil, who went into hiding with his wife and is reportedly seeking asylum, 'could not manage to get his daughter to join them'.
Referred to as the Day of the Shining Star, the occasion is celebrated with ice skating displays, flower shows, and laudatory tributes in state media, all reinforcing the underlying narrative.
S.Korea's government says that they were complying with the framework of sanctions on North Korea while pursuing exchange and cooperative projects with the North.
Kim Yong-chol's trip comes as expectations grow for a second US-North Korean summit after Kim Jong-un last week went to Beijing.
North Korea asked the United States to delay planned high-level talks in New York this week, a day after Washington abruptly announced the meeting's postponement.
The visit by Miguel Diaz-Canel comes amid stalled talks between North Korea and the United States.
Pertemuan terbaru akan diadakan di bahagian selatan perkampungan Panmunjom dalam Zon Bebas Tentera.
Pompeo departed from Tokyo, where he spent the first leg of a tour that will include stops in Pyongyang, South Korea and China.
Pompeo will spend less than a day on the ground in Pyongyang on Sunday meeting with Kim and seeking to flesh out US expectations for his regime to denuclearize.
It would also force an extraordinary level of cooperation between two Cold War foes that have no formal avenues for regular contact and are still technically at war.
A Seoul visit by Kim would be the first by a Northern leader since the partition of the peninsula decades ago after the end of the 1950-53 Korean War.
While Kim has stopped the missile launches and nuclear tests that rattled the world last year, he still retains the capability to strike the US homeland with a nuclear weapon.
Thousands of accompanying citizens waved bouquets and flags, chanting "Long live" to the leader.
The country's territory is largely composed of mountains and hills that have long been stripped bare for fuel or turned into terraced rice fields, allowing rainwater to flow downhill unchecked.
The two leaders will meet in the North Korean capital to discuss "practical measures to denuclearise" the peninsula, South Korean National Security Advisor Chung Eui-yong told reporters.
The North Korean leader says he is willing to cooperate with both Seoul and Washington on denuclearisation.
Moon and Kim have since agreed to hold a third summit in Pyongyang at an unspecified date in September.
Seoul proposed the envoy's visit Friday morning and Pyongyang accepted it a few hours later, a presidential spokesperson said, adding they had not yet decided who the envoy will be.
A diplomatic source speaking on condition of anonymity said Russia's objection stemmed mainly from the part that said North Korea had exceeded its 2018 oil import cap set by the 2017 sanctions.
Trump on Friday pulled the plug on the visit, blaming a lack of progress in denuclearisation efforts since his historic summit with North Korean leader Kim Jong Un in June.