South Korea is expecting the Democratic People's Republic of Korea to conduct a "surprise" nuclear test at an unpredictable time.  South Korea Defense Ministry says the DPRK could detonate its nuclear device at any time, and that Seoul is closely monitoring for this event.

South Korean and US intelligence authorities claim vehicle and personnel movements at a main DPRK nuclear test site were recently two to three times higher than last month's activities. Pyongyang launched nuclear tests at Punggye-ri, in northeastern DPRK.

The nuclear facility area is at Yongbyon, about 90 kilometers north the capital. Pyongyang has been raising tensions from early March on the Korean Peninsula by firing short- and medium-range missiles and artillery shells in a show of force against annual US-South Korea war drills. The DPRK considers these drills a dress rehearsal for northward invasion.