Kim Jong-un is increasing his underwater military capabilities and may even have plans in place to launch nuclear missiles from a submarine, it has been claimed.

There are fears the North Korean dictator is adapting his fleet of subs so they can fire warheads amid heightened tensions with the West.

It comes two years after 50 vessels, which account for 70 per cent of Pyongyang's submarines, disappeared off radar sparking panic in South Korea and Japan in the wake of a tense stand-off with South Korea.

Kim Jong-un (pictured in 2014) is increasing his underwater military capabilities and may even have plans in place to launch nuclear missiles from a submarine, it has been claimed

There are fears the North Korean dictator is adapting his fleet of subs so they can fire warheads amid heightened tensions with the West

It comes two years after 50 vessels, which account for 70 per cent of Pyongyang's submarines, disappeared off radar sparking panic in South Korea and Japan in the wake of a tense stand-off with South Korea

According to the Daily Express, 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.'

The subs disappeared from the radar following a military stand-off with the South.

At the time, the South Korean news agency Yonhap yesterday quoted a military official as saying the development was 'ominous' having earlier vowed to 'mobilise all our surveillance resources' to find the vessels.

Although security chiefs in Seoul later said it had noted the 're-appearance' of a large part of the submarine fleet, the statement suggested that some were still missing four days after they disappeared.

In December, terrifying satellite images emerged sparking fears that North Korea could be on the verge of strikes from a nuclear submarine.

The images, taken from above North Korea’s Sinpo South Shipyard, prompted suggestions that the weapon was preparing to go to sea.

Camouflage netting had been removed and supplies and equipment next to the vessel suggested it could be set to launch.

Expert Joseph Bermudez, from website 38 North, warned at the time: 'These two factors suggest that both craft may have recently been at sea or are preparing to go to sea in the near future.'

US military officials fear North Korea has placed a nuclear test in a tunnel with the potential to detonate it on Saturday. Pictured: North Korean leader Kim Jong Un (left) flanked by vice-chairman of the State Affairs Commission Choe Yong-Hae at an opening ceremony for 'Rymoyong street', a new housing development in Pyongyang today

North Korea has launched several missile tests this year, the latest on April 5 when it fired a ballistic missile into the sea off its east coast. It conducted its fifth nuclear test on September 9, 2016 (file picture)

He said that although the secretive state's intentions are unclear, the images suggest that North Korea is now capable of deploying missiles larger than a KN-11 submarine-launched ballistic missile which was tested in August.

It is believed that dictator Kim Jong-un’s nuclear submarine system is inspired by the Golf-class submarines used by the Soviet Union before the fall of the Iron Curtain.

This morning, Japanese Prime Minister Shinzo Abe said he feared Kim Jong-un 'has a capability' to fire missiles tipped with sarin - the same deadly gas used to kill 87 Syrian civilians in a horrifying gas attack last week.

That atrocity prompted the US to launch a surprise wave of missiles on one of dictator Bashar al-Assad's airbases.

Abe told a parliamentary session: 'There is a possibility that North Korea already has a capability to deliver missiles with sarin as warheads.'

Tensions on the Korean peninsula have escalated over Pyongyang's continued nuclear and missile testing programme, with the United States warning it could take unilateral action and sending a navy carrier group to near the Korean peninsula in a show of force aimed at deterring more tests.

North Korea marks the 105th anniversary of the birth of state founder Kim Il Sung on Saturday, North Korea's biggest national day called 'Day of the Sun'.

Leaders have in the past used the date to carry out weapons tests.

North Korea has launched several missile tests this year, the latest on April 5 when it fired a ballistic missile into the sea off its east coast. It conducted its fifth nuclear test on September 9, 2016.