North Korea makes progress on its first nuclear-powered submarine

North Korea released photographs Thursday showing what appears to be a largely completed nuclear-powered submarine hull, as leader Kim Jong-un blasted South Korea's push to acquire similar technology.

State media showed Kim inspecting a massive burgundy-coloured vessel coated with what appears to be anti-corrosion paint under construction inside an assembly hall. He was accompanied by senior officials and his daughter.

The Korean Central News Agency said Kim visited a shipyard to inspect construction of what North Korea describes as an 8,700-tonne nuclear-propelled submarine. The agency did not specify when the visit took place.

It was the first time North Korean state media released images of the submarine since March, when they mostly showed lower sections of the vessel.

Kim described South Korea's efforts to acquire a nuclear-powered submarine, which have been backed by US President Donald Trump, as an "offensive act" that severely violates the North's security and maritime sovereignty.

He said the South Korean plan demonstrates why North Korea's army needs to modernise and nuclear-arm, and claimed completion of his nuclear-powered submarine would be an "epoch-making" change in strengthening its nuclear deterrent.

Pyongyang has indicated it plans to arm the submarine with nuclear weapons, calling it a "strategic guided missile submarine" or a "strategic nuclear attack submarine".

Sophisticated weaponry wish list

Because submarines are typically built from the inside out, the release of what appears to be a largely completed hull suggests many core components, including the engine and possibly the reactor, are already in place, said Moon Keun-sik, a submarine expert at Seoul's Hanyang University.

"Showing the entire vessel now seems to indicate that most of the equipment has already been installed and it is just about ready to be launched into the water," said Moon, a former submarine officer in the South Korean navy.

Moon believes the North Korean submarine could possibly be tested at sea within months.

A nuclear-powered submarine was one item on a wish list of sophisticated weaponry that Kim announced during a political conference in 2021. Other weapons included solid-fuelled intercontinental ballistic missiles, hypersonic weapons, spy satellites and multi-warhead missiles.

North Korea has conducted tests to develop some of those systems and recently unveiled a new naval destroyer, which Kim hailed as a major step towards expanding the operational range and preemptive strike capabilities of the country's nuclear forces.

A submarine capable of operating stealthily for extended periods and launching missiles from underwater would be a worrying development for North Korea's neighbours, as such launches would be difficult to detect in advance.

Questions have persisted about whether North Korea, a heavily sanctioned country, could obtain resources and technology to build nuclear-powered submarines.

Some experts say North Korea's alignment with Russia — including sending thousands of troops and military equipment to support President Vladimir Putin's war in Ukraine — may have helped it receive technologies in return.

Whilst some analysts suspect North Korea may have sought a reactor from Russia, possibly from a retired Russian submarine, Moon said it is more likely North Korea designed its own reactor, whilst possibly receiving technological assistance from Russia.

South Korea's submarine plans

South Korean President Lee Jae Myung called for US support for South Korea's efforts to acquire nuclear-powered submarines during a summit with Trump in October, whilst reaffirming a commitment to increase defence spending.

Trump said the US is open to sharing closely held technology to allow South Korea to build a nuclear-powered submarine, but it is not immediately clear where and when the vessel would be built and how Seoul would obtain the nuclear fuel and reactor technology required.

KCNA said Kim on Wednesday supervised tests of new anti-air missiles fired into the sea. South Korea's Joint Chiefs of Staff said it detected the North launching several missiles from an eastern coastal town.

Tensions on the Korean peninsula have worsened in recent years as Kim accelerated his nuclear programme and deepened alignment with Moscow following Russia's full-scale invasion of Ukraine in early 2022.

His government has dismissed calls by Washington and Seoul to revive negotiations aimed at winding down his nuclear and missile programmes, which derailed in 2019 following a collapsed summit with Trump during his first term.