A top North Korean delegation led by the reclusive nation's second-most powerful person is visiting South Korea for the closing ceremony of the Asian Games at Incheon amid speculation over a lockdown in Pyongyang and a coup d'etat against Kim Jong-un.

The officials, Hwang Pyong-so, Choe Ryong-hae and Kim Yang-gon, who are not directly in-charge of the North Korean sports ministry, are in South Korea, hinting that Pyongyang may be willing to improve bilateral relations with Seoul.

South Korea's Unification Minister Ryoo Kihl-jae is scheduled to hold talks with the North Korean representatives who include nine others. They landed in South Korea's Incheon International Airport at about 10:00am local time.

Hwang is the director of the North Korean army's General Political Bureau and widely seen as the country's No 2, while Kim is chief of United Front Department of the ruling Worker's Party of Korea.

North Korean leader Kim Jong-un has been missing in public since 3 September reportedly due to ill health, adding fuel to the coup speculation.

Both South Korean and the US officials do not attach much credibility to the coup reports.

"We understand that Kim is suffering from a disease that resulted in oedemas and blisters on the joint. We were told the disease requires him to get treatment for a long period and that he needs surgery," a source told Yonhap news agency.