North Korea is building a new submarine class that could transport nuclear weapons closer to their targets, according to US intelligence. The new submarine will be the country's first operational naval vehicle capable of launching a ballistic missile.

While North Korea's ballistic missiles are advanced enough to reach the US territory of Guam, their submarine tech has always been considered rather crude and rudimentary, notes a report in Popular Mechanics.

As such, even if it is capable of firing a submarine-launched ballistic missile (SLBM), the country's lack of advanced stealth technology will allow it to be easily tracked and destroyed by the US and its allies like Japan and South Korea. In contrast, the American Ohio-class subs, for example, have allegedly never been tracked or detected by any enemy force until now.

North Korea's new submarine has been designated "Sinpo-C" by the US and its details were revealed to current affairs magazine The Diplomat this week.

The Sinpo-C appears to be a diesel-electric powered submarine. The 36ft wide warship with a displacement of 2,000 tons can reportedly carry two or more ballistic missiles.

North Korea currently has one ballistic missile submarine called the Gorae, designated Sinpo-B by US intelligence. The much smaller craft with a displacement of 1,700 tons can launch the Pukguksong-1 missile — a two-stage ballistic missile with a range of 745 miles. It is still not clear if it was this missile that was test-fired over Japan in August.

The Gorae, or Sinpo-B, could reportedly have been a test vehicle for the SLBM. The smaller submarine is believed to have never really left North Korean waters and could have only been used for missile testing.

That makes the Sinpo-C the first ballistic missile carrying submarine from North Korea. This sub could be capable of carrying and launching long-range missiles that are much larger, more capable and more destructive than the Pukguksong-1.