North Korea destroyed the most visible symbol of its nuclear weapons program on Friday, according to a news report, in a sign of its commitment to stop making plutonium for atomic bombs.
The reported demolition of the 20-metre tall cooling tower at its main reactor complex was a gesture in response to US concessions after the North delivered a declaration on Thursday of its nuclear programs under an agreement at international arms talks.
South Korean TV network MBC said the reactor blast occurred shortly after 4 pm (0700 GMT) before an audience of international TV cameras. There were no other immediate details. The symbolic explosion came just 20 months after Pyongyang shocked the world by detonating a nuclear bomb in an underground test to confirm its status as an atomic power.
The nuclear blast spurred an about-face in the US hard-line policy against Pyongyang, leading to the North's first steps to scale back its nuclear weapons development since the reactor became operational in 1986.
Last year, the North switched off the reactor at Yongbyon, some 60 miles (100 kilometers) north of the capital of Pyongyang, and it has already begun disabling the facility under the watch of US experts so that it cannot easily be restarted.
The destruction of the cooling tower, which carries off waste heat to the atmosphere, is another step forward but not the most technically significant, because it is a simple piece of equipment that would be easy to rebuild.
Still, the demolition offers the most photogenic moment yet in the disarmament negotiations that have dragged on for more than five years and suffered repeated deadlocks and delays. Those attending the event include the top US State Department expert on the Koreas, Sung Kim, along with broadcasters from the United States, China, Japan, Russia and South Korea.
North Korea's nuclear declaration, which was delivered six months later than the country promised and has not yet been released publicly, is said to only give the overall figure for how much plutonium was produced at Yongbyon, but no details of bombs that may have been made.
The declaration was being distributed Friday by China, the chair of the arms talks, to the other countries involved, US envoy Christopher Hill said in Kyoto, Japan.