North Korea carried out an underground test of a nuclear bomb equivalent to 5000-15,000 tons of TNT according to the Russian Defense Minister. (The bomb dropped on Hiroshima was approximately 15,000 tons of TNT.) Staunch NK ally China branded the test "brazen" and voiced its "resolute opposition." Japanese PM Shinzo Abe called the NK action "unpardonable" and stated that the region was "entering a new, dangerous nuclear age." In a statement from the White House, President Bush would not verify that NK had tested a nuclear bomb but he did affirm American intentions to fulfill its security commitments in the region and to hold NK responsible for the transference of nuclear material or weapons. Concerns are now that South Korea and Japan will seek to enter the exclusive nuclear club of nine now known to possess nuclear weapons.
Cf. http://news.bbc.co.uk/2/hi/asia-pacific/6032525.stm; http://www.foxnews.com/story/0,2933,218699,00.html; and FNC F&F.