SEOUL, April 22 (Xinhua) -- South Korea's Defense Ministry on Tuesday warned of a "surprise" nuclear test of the Democratic People's Republic of Korea (DPRK) citing increased activity in its main underground test site.
Defense Ministry spokesman Kim Min-seok told a routine press briefing that a lot of activity has been detected in and around the Punggye-ri test site in the northeastern DPRK where its third test was conducted in February last year.
He declined to elaborate on what activities are being made near the test site, citing an intelligence sharing pact with the United States.
But, local media reported quoting military officials that the site has recently been cloaked by fence screens and many vehicles were coming in and out of the place.
"Our military is thinking of possibilities that North Korea ( DPRK) may stage a nuclear test by surprise in the short term and that pretend to conduct a test as seen in past cases," said the spokesman.
Kim said verbal threats have been heard recently from the DPRK, declining to unveil where it got sources. Among the bellicose rhetorics were "ready to take next steps that enemies can never think of" and "a great thing will take place before April 30."
The warning came ahead of U.S. President Barack Obama's trip to Asia. Obama is scheduled to arrive in South Korea on Friday for a two-day trip after staying in Japan for three days. The week-long tour will also see the president visit Malaysia and the Philippines.
Concerns emerged that the DPRK may seek provocations, including its fourth nuclear test, when Obama came to Asia, but skepticism remained on such expectations given political risks and burdens that Pyongyang will shoulder following the nuclear detonation.
After the DPRK fired two Rodong medium-range ballistic missiles on March 26, the UN Security Council held an extraordinary session, censuring its violation of UN resolutions that have banned Pyongyang from testing ballistic missile technology.
In response, the DPRK's Foreign Ministry issued a warning on March 30, saying that it would "not rule out a new form of nuclear test" to bolster up its nuclear deterrence, accusing the United States of "acting rashly" at the UN Security Council.
Defense Minister Kim Kwan-jin said in February that preparations for the DPRK's another nuclear test were already completed, noting that nuclear tests and long-range missile launches could be carried out at any time upon the decision of the DPRK leadership.
The top military official added nuclear tests and missile launches were correlated as seen in past cases.
The DPRK conducted its first nuclear test in October 2006, three months after firing the Rodong missiles. In May 2009, Pyongyang staged its second nuclear test, just two months before firing off other Rodong missiles.
The third test was carried out last February, two months after Pyongyang launched the three-stage rocket called Unha-3, which Seoul claimed was a long-range missile.
The DPRK launched the mid-range missiles after firing a volley of short-range missiles and rocket-propelled shells in the past. But, the long-range rockets had yet to be test-fired, easing worries about the fourth nuclear test.
The DPRK has entered a phase of carrying out a surprise nuclear test on short notice from its leadership at any time, the Defense Ministry spokesman said.
On Monday morning, the ministry launched a special task force with the Joint Chiefs of Staff to step up efforts to monitor and brace for possible DPRK nuclear detonation.