North Korean soldiers watch the South Korean side from a lookout tower at their observation post in the demilitarized zone (DMZ) separating the two Koreas, December 28, 2011.

Three defections across the heavily fortified Demilitarized Zone separating North and South Korea are raising questions about the global flashpoint.
 

South Korean officials said three North Korean defectors have sneaked across the DMZ in the past three months, one of them announcing his arrival by knocking on the door of a South Korean barracks.