By John Sudworth
BBC News, Seoul
A new star appeared in the sky when Kim Jong-il was born, biographers say
North Korea has announced that it has made significant progress towards the development of thermo-nuclear power.
It is a claim that is likely to be met with some scepticism.
Despite hopes that the technology can produce large quantities of cheap, clean energy, no country has so far succeeded in making it work.
North Korea is one of the world's poorest countries and struggles to generate enough electricity for lighting and other basic needs.
The statement, carried by North Korea's official state media, said the country's scientists had succeeded in carrying out nuclear fusion.
Laboratory demonstrations of the process, known to release large amounts of energy, are nothing new.
But the North Koreans appear to be claiming to have gone much further, by building what they describe as a "unique thermo-nuclear reaction device".
The dream of overcoming the huge technical challenges to make nuclear fusion commercially viable has so far eluded scientists in Europe, America and China, but they continue to try because the prize is so great: a cheap and abundant source of energy with little environmental impact.
North Korea's claim that it has completed the fundamental research, putting the technology within its grasp, will be dismissed as highly unlikely unless concrete evidence is produced.
Pyongyang says its latest scientific breakthrough coincides with the birthday of the country's founder, and eternal president Kim Il-sung - not the first time it seems that the laws of nature have been bent in his honour.
According to official biographies, when his son, the current leader Kim Jong-il was born, a new star appeared in the sky.