UPDATE: North Korea has moved a long-range rocket to its launch pad in what is clearly a show of force that is meant to overshadow the nuclear security summit taking place in South Korea's capital. The transportation by specially equipped railway cars of the so-called space rocket--really a ballistic missile--was observed by a U.S. satellite.
There is no telling what North Korea might do at any moment. Kimist North Korea is the most dangerous and unpredictable country on the planet, more dangerous, even, than its partner in proliferation, Islamist Iran, which is probably funding Pyongyang's planned ballistic missile launch in order to divert attention from the mullahocracy's nuclear program.
All kinds of aggressive acts and provocations on the part of North Korea are possible, including, in addition to the aforementioned, long-range missile launch, which is scheduled for mid-April, a new nuclear test and actual attacks on South Korean targets.
From Pyongyang's point of view, this week's nuclear summit in Seoul, South Korea, U.S. President Barack Obama's warning about the North's pursuit of nuclear weapons, and South Korea's warning that it might shoot down the North's missile if it passes over South Korean territory are acts of aggression, or, at the very least, useful pretexts for proving to the world that the North's "Military First" policy is still very much in effect following the death of Dear Leader Kim Jong Il.