The pariah nation "is on an aggressive schedule to build and deploy its first operational ballistic missile submarine," said a Thursday note on 38North, a project of the US-Korea Institute at Johns Hopkins School of Advanced International Studies.

Strategists anticipated such a development after Pyongyang began testing submarine-launched ballistic missiles, or SLBMs, last year. Under dictator Kim Jong Un, the country's nuclear weapons program has made great technological advances and has signaled a willingness to use submarines for offensive military action.

Commercial satellite imagery from Nov. 5 shows sections of a pressure hull — the inner casing of a submarine that's designed to withstand the intense underwater pressures — in a shipyard located within the North Korean port city of Sinpo, the 38North note said. That likely means construction of a new vessel, possibly the SINPO-C ballistic missile submarine.

Such a watercraft would be the logical follow-up to the North's current ballistic missile submarine, which is experimental in nature, the note continued.