“The DPRK would never remain an idle onlooker to the naval and underwater military activities of the enemies seriously threatening the sovereignty and interests of the DPRK by constantly deploying large numbers of strategic assets,” Kim was quoted as saying by the official Korean Central News Agency today.

DPRK stands for the Democratic People’s Republic of Korea, the nation’s official name.

It wasn’t clear when Kim visited the shipyard or where it was located.

The report was published in the run-up to US and South Korean forces staging joint exercises.

Their training from March 10 to March 20 is designed to strengthen combat readiness.

In addition to developing nuclear-tipped missiles, North Korea has sought to beef up the development of other strategic assets such as submarines.

Its increased military ties with Russia have also alarmed South Korea and the US, prompting the allies to factor that risk into their upcoming drills.