North Korea to "restart Yongbyon nuclear reactor" North Korea says it is restarting its main nuclear facility Yongbyon. The site includes a nuclear reactor, a source of plutonium that could be used for nuclear weapons. The announcement is the latest in a series of provocative moves by Pyongyang that have angered the international community. North Korea carried out a third nuclear test in February and was slapped with increased UN sanctions. Since then, it has threatened to strike both US and South Korean targets. Seoul's concerned by Pyongyang's announcement that it is restarting activities at Yongbyong. South Korean Foreign Ministry Spokesman Chao Tai-Young said: "If the report is true, it's really regrettable. North Korea should keep to its promise and its agreements. It should stick to the denuclearisation of the Korean peninsula. Our government will closely monitor the situation. The US is also watching closely and has responded to Pyongyang's escalating war rhetoric - with high-profile movements of advanced aircraft and warships around the Korean peninsula. The move to restart the reactor comes as a big blow to China's stated aim of restarting de-nuclearisation talks on the Korean peninsula, prompting a foreign ministry spokesman in Beijing to express regret at the decision. It was unclear how quickly the Yongbyon plant, whose cooling tower was destroyed as part of a de-nuclearisation deal, would take to restart and it was impossible to verify whether it was still connected to North Korea's antiquated electricity grid at all. It was a reactor that was nearing obsolescence with a cooling tower that wasn't functioning properly when it was blown up. It could mean they've been rebuilding quite a few things," said Yoo Ho-yeol, North Korea specialist at Korea University in Seoul. with agencies More about: Korea crisis, North Korea, South Korea