Kim Chang-son, known as North Korean leader Kim Jong-un's de facto chief of staff, sitting in a car after inspecting Sofitel Legend Metropole Hanoi Hotel, Saturday. Yonhap

A senior North Korean official is believed to have looked around areas near a smartphone factory in Vietnam owned by South Korean tech giant Samsung Electronics Co., sources said Sunday.

Kim Chang-son, known as North Korean leader Kim Jong-un's de facto chief of staff, and other officials arrived in Hanoi Saturday to check logistics for a second summit between the United States and North Korea slated for Feb. 27-28.

The Kim delegation left the Vietnamese government's guest house in Hanoi at around 7 a.m. and headed north to the Bac Ninh province where a smartphone-producing line by Samsung Electronics is located, according to sources.

The group is believed to have driven around the areas surrounding the factory and assessed the routes to and from Hanoi. It also visited Thai Nguyen province in the northeast region where another Samsung smartphone factory is located.