Updated

South Korea's intelligence authorities were closely monitoring "suspicious movement" at another North Korean site Monday night in the northeast part of the country, according to a report by the Yonhap News Agency based in Seoul.

Intelligency officials reportedly were watching Punggye-ri in North Hamgyeong Province, and had spotted up to 40 personnel and vehicles moving around the area, Yonhap quoted Kim Seung-kyu, South Korea's chief intelligence official.

"We are closely watching whether Pyongyang intends to conduct another nuclear test," Kim said.