While is still struggling to develop nuclear-headed airborne missiles, it is fast increasing its underwater military power.

The country possess numerous submarines, which it has used with devastating effect in the past, with fears they are now being adapted to fire nuclear weapons.

Even more worrying is the submarines’ ability to ‘disappear’ and avoid detection. In 2015 around 50 went missing, setting alarm bells ringing in Seoul and Tokyo.

Security expert Bruce Klingner told CNBC: “We didn’t know where they were at the time. One would hope that we would keep very close tabs on those that could launch the submarine-launched ballistic missiles [SLBMs].

“All of that is very worrisome because that may very well have a nuclear weapon someday.”

Being able to launch an attack from a submarine, rather than a static site somewhere in North Korea, opens up ’s enemies to a new sort of risk.

Mr Klinger explained an attack from the ocean would take South Korea by surprise, due to the country’s defences geared towards an attack over the border.

He said: “The problem with the SLBM is that it exposes South Korea’s flanks to attack.”

Submarines have already been used by the North Korean military to deadly effect, most recently in 2009 when a North Korea submarine sunk a South Korean navy vessel, killing 46 people.

Adding nuclear weaponry to the mix would prove disastrous to country’s across east Asia.

North Korea warREUTERS

North Korea has around 50 submarines and is feared to be developing them for nuclear war

Other military experts warned of the devastating North Korea could cause using nuclear submarines.

Nicholas Eberstadt of the American Enterprise Institute think tank said: “Their conventional forces maybe not very capable at the moment, but they have a lot of weapons of mass destruction. CONTINUE…