North Korea appears to be striving to reinforce its underwater warfare capabilities with a focus on developing submarine-based missiles, which military analysts say would pose a serious security threat given the difficulties in detecting and tracking them.

Recent commercial satellite imagery indicated that the conning tower of a new North Korean submarine housed one or two possible vertical launch tubes for either ballistic or cruise missiles, the U.S.-based research blog 38 North said in its latest analysis on Thursday.

“The boat could serve as an experimental test bed for land-attack missile technology, which if successful, may be integrated into a new class of submarines,” said 38 North, which is run by the U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies.

The website also said imagery over the past six months indicated that Pyongyang has been upgrading facilities at the Sinpo South Shipyard in preparation for a significant naval construction program, possibly related to submarine development.

Although the threat from the regime’s development of submarine-launched ballistic missiles will be grave, complicating regional missile defense planning, deployment and operations, the site said such a threat is not yet present today.

“Moreover, an effort by Pyongyang to develop an operational missile-carrying submarine would be an expensive and time-consuming endeavor with no guarantee of success,” it noted.

The website added what missile system would be used for submarine operations is still speculative for now, but the possibilities include a shorter naval version of the Musudan intermediate-range ballistic missile, a Rodong medium-range ballistic missile, naval versions of the KN-02 short-range ballistic missile or a totally new system.

Amid increasing concerns over the North’s SLBM capabilities, Seoul’s Defense Ministry, for the first time, mentioned the North’s development of the SLBM in its 2014 defense white paper published Tuesday.

“North Korea has been bolstering its underwater attack capabilities though constantly seeking to build new types of submarines including those that can carry ballistic missiles,” said the biennial defense policy paper.

The white paper also noted that the North is presumed to have secured the missile capability to threaten the U.S. mainland through five long-range rocket tests. Experts have said that its ballistic missile, tested in December 2012, appeared to have a range of 10,000 kilometers ― far enough to strike the U.S. mainland.

South Korean experts argue that given the size and technological capacity of North Korean submarines, Pyongyang has yet to reach a level to mount ballistic missiles on its submarines. But they said the South should be ready for any threats given the unpredictable, opaque nature of the regime.

Fears about the SLBM stem from the North’s potential “second-strike capability” to launch an overwhelming nuclear retaliation if it suffers a first strike from enemy forces.

The second-strike capability forms the basis of a condition referred to as “mutual assured destruction” that maintained the “balance of terror” during the Cold War era. Submarine-launched ballistic missiles are at the core of the capability as submarines can launch targeted stealthy attacks on enemy forces.

Stephen Walt, an international relations theorist at Harvard University, expressed doubts whether the North’s SLBM would give the country second-strike capability.

“I am not that concerned about this possibility, because a submarine-launched missile provides a second capability only if the submarine itself cannot be detected, tracked and attacked,” he told The Korea Herald. “That is unlikely to be true of any small submarine force that North Korea might develop.”

By Song Sang-ho (sshluck@heraldcorp.com)