North Korean leader Kim Jong Un has claimed the country has developed a hydrogen bomb - but outside experts are skeptical.
According to the state-controlled Korean Central News Agency, Mr Kim made the comments as he toured the Phyongchon Revolutionary Site - which is dedicated to his father and grandfather, Kim Il Jong and Kim Il Sung, who ruled before him.
Mr Kim claimed the regime's founder Kim Il Sung “turned the DPRK (Democratic People’s Republic of Korea) into a powerful nuclear weapons state ready to detonate a self-reliant A-bomb and H-bomb to reliably defend its sovereignty and the dignity of the nation”.
A hydrogen bomb is far more powerful than an atomic bomb and needs more advanced technology to be produced.
Experts are skeptical that the so-called Hermit Kingdom - which reportedly suffered a severe famine earlier this year - would have the capabilities to produce such a weapon.
Dr Jeffrey Lewis from the Middlebury Institute of International Studies in Monterey, California said it was “unlikely” they actually had developed the weapon but warned: “I don’t expect them to keep testing basic devices indefinitely either”.
A South Korean intelligence official told the Yonhap news agency that Mr Kim’s comments were probably just rhetoric.
North and South Korea are technically still at war as their 1950-153 war ended in a truce rather than peace treaty.
Tensions between the two countries flared in August after North Korean soldiers fired shots into the demilitarised zone on the border.
In was reportedly in response to a South Korean loudspeaker that had been blaring anti-Pyongyang propaganda.
North Korea carried out underground nuclear tests in 2006, 2009 and 2013 and has been subject to UN Security Council sanctions banning all trade and finance activities that aid its weapons programme.