SEOUL: North Korean leader Kim Jong Un inspected warships at a shipyard in a renewed drive to bolster his naval forces as his country ramps up "war preparations," state media said on Friday.

"The strengthening of the naval force presents itself as the most important issue in reliably defending the maritime sovereignty of the country and stepping up the war preparations at present," Kim said at the Nampho Dockyard, according to the Korean Central News Agency.

In recent weeks, Kim has declared South Korea his country's "principal enemy," jettisoned agencies dedicated to reunification and outreach, and threatened war over "even 0.001 mm" of territorial infringement.

He also hailed the test launch of a new strategic cruise missile from a submarine, calling it a key moment in the development of the North's naval power.

A nuclear-powered submarine was on Kim's strategic weapons wish list set out at a key party congress in 2021, along with a hypersonic warhead, spy satellites and solid-fuel intercontinental ballistic missiles.

During his visit to the Nampho shipbuilding base, about 65 kilometers southwest of Pyongyang, Kim was briefed on various warships under construction as well as preparations for a "new huge plan" assigned by the ruling party.

No details of the plan were provided.

Kim "expressed expectation that the workers of the dockyard would successfully build on the world level the major warships," KCNA said.

North Korea last year launched what it called its first "tactical nuclear attack submarine," which Seoul's military at the time said did not look to be operational.

Analysts said the vessel appeared to be modified from an existing diesel-electric submarine originally designed in the 1950s, and have posed questions about its limitations and vulnerabilities as a platform.

Meanwhile, North Korea fired multiple cruise missiles Friday, Seoul's military said, continuing a fresh streak of weapons testing as Kim Jong Un's regime ramps up what it calls "war preparations."

Pyongyang has also carried out ever more weapons tests, including multiple cruise missile launches, an "underwater nuclear weapon system" test, plus firing a solid-fueled hypersonic ballistic missile.

On Friday, Seoul's Joint Chiefs of Staff said the military had "detected at around 11 a.m. (0200 GMT) the firing of multiple unidentified cruise missiles" into the sea off the country's west coast.

The South Korean military has "stepped up surveillance in close coordination with the United States," the JCS said in the statement.

The military is "closely monitoring for signs of additional activity" by the North Korean army, it said, adding they were "closely analyzing" the launch.

Unlike their ballistic counterparts, the testing of cruise missiles is not banned under current UN sanctions on Pyongyang.