Seoul expects 'surprise' Pyongyang n-test at unpredictable time

South Korea's military on Tuesday expected North Korea to conduct a "surprise" nuclear test at an unpredictable time as seen in the case of its previous nuclear detonation.

"As seen in North Korea's recent fourth nuclear test, there is a possibility for (a fifth nuclear test) taking place by surprise at a time which we can hardly predict," Xinhua quoted Defence Ministry spokesman Moon Sang-Kyun as saying.

Moon said North Korea has prepared to detonate its nuclear device at any time and can actually do it when the country makes a decision, noting that the South Korean military is closely monitoring a surprise detonation.

According to South Korean and the US intelligence authorities, the movement of vehicles and personnel at a main North Korean nuclear test site recently increased two to three times more than last month.

South Korean President Park Geun-hye also warned on Monday of possible nuclear provocation, saying that Pyongyang can conduct any type of abrupt provocations to break away from isolation and consolidate the regime following tougher sanctions toward the country.

Tougher-than-ever sanctions on Pyongyang were adopted at the UN Security Council in early March over North Korea's fourth nuclear test and long-range rocket launch.

North Korea detonated what it claimed was its first hydrogen bomb on January 6, followed by the launch of a long-range rocket, which was condemned as a disguised test of ballistic missile technology, on February 7.