Underwater Test-fire of Korean-style Powerful Strategic Submarine Ballistic Missile | 38 North: Informed Analysis of North Korea

The imagery and information released by KCNA would lead an observer to conclude that this recent test was conducted from the SINPO-class experimental ballistic missile submarine based at the Sinpo South Shipyard. This, however, may be incorrect … It would appear to be more reasonably in line with assessed North Korean capabilities, however, that the test launch was conducted from a submerged barge—possibly the one seen at the Sinpo South Naval Shipyard.

Source: Underwater Test-fire of Korean-style Powerful Strategic Submarine Ballistic Missile | 38 North: Informed Analysis of North Korea