North Korea appears to be building its first operational ballistic missile submarine.

Satellite images analyzed by 38 North seem to indicate that construction of such a vessel is well underway at the Sinpo South Shipyard. Photos show what appear to be sections of a pressure hull for what could be the Sinpo-C diesel-electric ballistic missile submarine. The vessel is a the follow-on to the current Sinpo-class experimental ballistic missile submarine that was used to test North Korea’s submarine launched ballistic missile (SLBM) capability.

“Imagery from November 5 shows two larger circular objects that may be sections of a submarine’s pressure hull,” the 38 North analysis reads. “The diameter of the first object is approximately 7.1 meters, while the diameter of the second starts at approximately 7.1 meters and reduces to approximately 6.1 meters. The larger object has what appears to be two internal cross members that could be used to support decks or internal equipment.”

RECOMMENDED: How the U.S. Navy Could Crush China in a War

The 38 North analyses suggest that the new SSB—called the Sinpo-C—is somewhat larger than North Korea’s Soviet-developed 1950s-era Project 633 Romeo-class diesel electric attack submarines. North Korea has 20 of the antiquated Romeo-class boats in its fleet.

As Ankit Panda at The Diplomat reports, the Sinpo-C could have a submerged displacement greater than 2,000 tons and will likely be the largest vessel ever to be built for the Korean People’s Navy since the Najin-class frigates. It is likely that both the Sinpo-B (Gorae-class) and the Sinpo-C are derived from the elderly Russia submarine’s technology—which ultimately derives from the World War Two-era German Type XXI submarine.

RECOMMENDED: How America Would Wage a War Against North Korea 

The Sinpo-B does not appear to be an operational SSB. The vessel, which displaces about 2000-tons underwater, appears to be a test platform for the Pukguksong-1 SLBM and other follow-on missiles. Indeed, Pyongyang appears to be continuing ejection testing at shore facility near the shipyard where the Simpo-C is being built.

“The continued presence of this object suggests ongoing SLBM ejection tests. If correct, this is likely a continuation of the ejection test campaign reported during July of this year,” the 38 North analysis reads. “Regardless, additional ejection tests should be expected in the future for further development of the Pukguksong-1, a potential Pukguksong-3, or other future SLBMs. Such a test would also be valuable for validating missile launch systems for a new class of SSBs.”

RECOMMENDED: North Korea Has 200,000 Soldiers in Its Special Forces 

While the new Sinpo-C SSB and its missile are not exactly state of the art compared to the United States or Russian nuclear-powered ballistic missile submarines like the Ohio-class or the Borei, the addition of nuclear-armed submarines would increase the overall survivability of the North Korean nuclear arsenal once the vessels are fielded in sufficient numbers. South Korean and American forces would have to assign additional submarines to find and track the North Korean boomers. Essentially, the vessels complicate the targeting problem for the U.S. and its allies.

At the end of the day, neither the Sinpo-B or Sinpo-C are particularly impressive vessels. However, it is nonetheless impressive that an impoverished and technologically backward state with primitive industrial capabilities developed and built its own ballistic missile submarine. It should be a reminder that North Korea might not be quite the pushover that some might imagine it to be.

Dave Majumdar is the defense editor of The National Interest. You can follow him on Twitter @DaveMajumdar.

Image: Reuters.