This would be a big development if true, however with the decrepit state of its submarine fleet it is doubtful this is a real functional wartime capability for the Kim regime:
This photo, carried by North Korea’s official Korean Central News Agency on Jan. 29, 2024, shows the North’s firing of submarine-launched cruise missiles the previous day.
North Korean leader Kim Jong-un has overseen the test-fire of submarine-launched cruise missiles and reviewed a project to build a nuclear-powered submarine, state media reported Monday.
The new Pulhwasal-3-31 strategic cruise missile precisely hit an island target after flying over the East Sea for 7,421 seconds and 7,445 seconds, the Korean Central News Agency (KCNA) said, suggesting the test involved two missiles.
The flight time translates to two hours, three minutes and 41 seconds, and two hours, four minutes and five seconds, respectively. The KCNA did not give further details, including whether the missiles were launched from a submarine or a barge and how far they flew.
Yonhap
Kim Jong-un made sure to throw in the word “nuclear” to get the media’s attention:
Kim stressed Sunday that “the nuclear weaponization of the navy is an urgent task of the times and a core requirement for building the state nuclear strategic force,” the KCNA said.
“He set forth the important tasks arising in realizing the nuclear weaponization of the navy and expanding the sphere of operation of the state nuclear deterrence in a diversified way,” it said.
South Korea’s Joint Chiefs of Staff said Monday it is weighing the possibility that North Korea might have “exaggerated” information on the missile’s flight time, adding that it is analyzing details of the launch platform.
The latest launch came as North Korea has been diversifying missile launch platforms to deliver nuclear weapons in a bid to bolster its capabilities to stage a surprise attack and evade the existing missile defense system.
You can read more at the link, but the ROK is probably right that this test is exagerated. However, it is clear what they are working towards because a submarine with cruise missiles would pose a challenge to missile defenses because you don’t know where it is to direct your missile defense radars against.