North Korea tests underwater nuclear weapon amid soaring tensions with South

North Korea said it conducted an "important" test of its underwater nuclear weapons system off the nation’s east coast amid fresh tensions with South Korea.

The test of the "Haeil-5-23" system was carried out by the defence ministry's think tank, reported state media KCNA, without specifying a date. Haeil, which means tsunami, is a name the North has given to its nuclear-capable underwater attack drones.

The alleged nuclear attack drone, which was first tested in March 2023 is among a broad range of weapon systems demonstrated in recent years amid fears of Kim Jong-un expanding his nuclear-capable weapons arsenal.

The latest test was reportedly conducted in protest against this week's joint military drills by South Korea, the US and Japan, whom the North have accused of "getting frantic with military exercises".

The three allies held their three-day regular drills until Wednesday, alongside the US aircraft carrier Carl Vinson, as part of efforts to improve their responses to Pyongyang's evolving nuclear and missile threats.

An unnamed North Korean defence ministry spokesperson threatened the three nations of "catastrophic consequences", according to the state media.

"Our army's underwater nuke-based countering posture is being further rounded off and its various maritime and underwater responsive actions will continue to deter the hostile military manoeuvres ...," the spokesperson added.

"We strongly denounce the US and its followers for their reckless acts of seriously threatening the security of the DPRK (Democratic People's Republic of Korea) from the outset of the year and sternly warn them of the catastrophic consequences to be entailed by them."

The state television aired previous atmospheric explosion tests, which have been monitored by US and South Korean authorities, but the reported underwater weapon has not been independently verified.

The alleged drone test followed Mr Kim's declaration of scrapping his country's long-standing goal of a peaceful unification with South Korea. He threatened to rewrite the North's constitution to define the South as its most hostile foreign adversary, in a move that would further damage the fragile relation between the nations.

The relations between the two Koreas have torpedoed to the worst in recent history following Mr Kim’s rare visit to Russia and the subsequent launch of North Korea’s spy satellite into orbit last year in November.

The historic step to discard the decades-long pursuit of a peaceful unification, which was based on a sense of national homogeneity shared by both Koreas, comes at at time when Pyongyang is strengthening its partnerships with Moscow and Beijing.

The closer ties with Russia and China are seen as attempts to break out of diplomatic isolation and create a united front against the West.

South Korea on Thursday called on the UN Security Council “to break the silence” over the North's escalating missile tests and threats. “It’s a big question,” South Korea’s UN ambassador Hwang Joonkook told reporters after an emergency closed meeting of the council on the North’s first ballistic missile test of 2024.