SEOUL (AFP) - North Korea could well be preparing to carry out its fourth nuclear test, South Korea's Defence Ministry said on Tuesday, citing a significant step up in activity at the North's main test site.
"Our military is currently detecting a lot of activity in and around the Punggye-ri nuclear test site," ministry spokesman Kim Min-Seok told a press briefing.
"We are thinking of possibilities that the North may stage a surprise nuclear test or just pretend to stage a nuclear test," Kim said, adding that the Joint Chiefs of Staff had set up a special task force in case Pyongyang goes ahead with an underground detonation.
US President Barack Obama is due to arrive in South Korea on Friday for a two-day visit, and there has been widespread speculation that the North may stage a provocation to coincide with the trip.
Kim stressed that North Korea's nuclear weapons programme was at a stage where it could conduct a test "at any moment" once the order was given by the leadership in Pyongyang.
North Korea has so far carried out three nuclear tests in 2006, 2009 and 2013.