A nuclear expert claimed that North Korea is developing a deadly H-Bomb, with fears that it could be heading towards the US.

Pyongyang has showed its capability to produce hydrogen-3, a radioactive isotope of hydrogen also called tritium, which is "necessary for a hydrogen bomb to create fusion," Professor Siegfried Hecker from Stanford University said.

"The evidence is quite clear that North Korea is able to produce tritium," he said, noting that the North Korean military now has the "basic element" needed to make thermonuclear weapons like the H-Bomb.

The professor visited Pyongyang leader Kim Jong-un's uranium-enrichment facility in Yongbyon during a trip in North Korea in 2010.

 "I believe they have made tritium. In fact, last year there have been some indications that they were trying to market one of the key ingredients for making tritium, something called lithium-6," Hecker said. "So it's clear they know how to make tritium. We know that's official."

Hecker also noted that commercial satellite imagery revealed that Pyongyang is adding at least one more tritium production facility.

However, he said that "it takes much more than that to weaponize hydrogen bombs. I don't believe they can do that [yet]."

DPRK Today reported last March 2016 that Pyongyang created an "H-Bomb" that is "much bigger than the one developed by the Soviet Union." According to Sputnik News, if the warhead is attached to an intercontinental ballistic missile, it would "fall on Manhattan in New York City, [and] all the people would be killed instantly."

The Hermit Kingdom in January 2016 claimed that it test-fired a hydrogen bomb, although this has not been confirmed.

Hecker estimated that the DPRK's nuclear warhead stockpile stands to around 25 and that the country could produce between six and seven more each year, Yonhap News reported.