North Korean leader Kim Jong Un is suggesting his isolated regime has developed a hydrogen bomb.
Kim was quoted Thursday by the official KCNA news agency saying North Korea is now "a powerful nuclear weapons state ready to detonate a self-reliant A (atomic)-bomb and H-bomb to reliably defend its sovereignty."
KCNA said Kim made the comments while touring Phyongchon Revolutionary Site, a historic military site, in Pyongyang.
A hydrogen bomb, also known as a thermonuclear bomb, is far more powerful than an atomic bomb because of the advanced technology involved.
South Korea's Yonhap news agency said it was told by an official with the country's intelligence agency that there is no evidence to support Kim's claims.
North Korea is under strict economic sanctions imposed by the United Nations Security Council for conducting three underground nuclear tests in 2006, 2009 and 2013.