North Korea may have developed a hydrogen bomb, and its leader Kim Jong-un warned that he is ready to use A-bombs and H-bombs to protect the isolated country.
Hydrogen bombs are more powerful that atomic bombs as it uses nuclear fusion to create an explosion.
"North Korea is a powerful nuclear weapons state ready to detonate self-reliant A-bomb and H-bomb to reliably defend its sovereignty," Kim reportedly said during an inspection tour to an arms plant in Pyongyang.
Kim Jong-un's announcement was published by North Korean news agency KCNA on Thursday.
However, North Korea's claims have not been verified and it is often known to make false or exaggerated claims of its nuclear and military capabilities.
Intelligence experts in South Korea, the chief rival of its neighbour, have dismissed Kim's statement as 'rhetoric'.
"We do not believe that North Korea, which has not succeeded in miniaturizing nuclear bombs, has the technology to produce an H-bomb," an intelligence official told Yonhap News.
Earlier this year, the Kim Jong-un regime claimed that it had the technology to make miniaturised nuclear weapons that can be fitted on to missiles.
North Korea had vowed to enhance its nuclear power this year after claiming that the United States was planning to invade the country under the 'guise' of human rights abuses.