South Korea's military has confirmed the possibility that North Korea is building a submarine capable of launching ballistic missiles.

In a report to Rep. Jin Sung-joon of the main opposition New Politics Alliance for Democracy, the Joint Chief of Staff (JCS) said Sunday that it has detected signs of the North's development of a submarine-launched ballistic missile (SLBM).
 
The JSC added that South Korea and the United States are jointly scrutinizing the North's related move.
 
A senior South Korean government source said the South Korean and U.S. intelligence agencies spotted signs that the North has developed a ballistic missile launch tube for submarines.
 
The intelligence agencies are closely monitoring the North’s move as they believe that if the North succeeds in a test fire of a SLBM, it could build 3,000-ton Golf-class submarines equipped with ballistic missiles.