N Korea showed US scientist 'vast new nuclear facility'
An American nuclear scientist says he was shown a vast new nuclear facility when he visited North Korea last week.
Dr Siegfried Hecker said he had been shown "more than 1,000 centrifuges" for enriching uranium, which can be used for making nuclear weapons.
The Stanford University scientist was stunned at how sophisticated the plant was, according to reported remarks.
When international weapons inspectors were expelled from North Korea in 2009, the plant did not exist, officials say.
Dr Hecker's discovery was first reported in the New York Times, where he spoke of being taken to see an "ultra-modern control room".
In subsequent remarks obtained by AP news agency, he said that unlike other North Korean facilities it "would fit into any modern American processing facility", and spoke of more than 1,000 centrifuges "all neatly aligned and plumbed below us".
He said the facilities appeared to be primarily for civilian nuclear power - and he saw no evidence of plutonium production.
But Dr Hecker said the new facilities he viewed "could be readily converted to produce highly enriched uranium bomb fuel", AP reported.
The North is believed to have weaponised enough plutonium for at least six atomic bombs but is not known to have a uranium-based weapons programme.
He did not specify exactly where the new facility was located, but he said he had been taken to it during a visit to North Korea's main nuclear complex at Yongbyon, about 100km (60 miles) north of the capital Pyongyang.
Dr Hecker - the 67-year-old former head of the Los Alamos Nuclear Laboratory - earlier also backed up claims that, in a separate advance, North Korea is constructing a light-water nuclear reactor.
New satellite images appear to show the reactor being built at Yongbyon.
Light-water reactors are primarily for civilian energy purposes but require uranium to be enriched for use in them - uranium that could then be further enriched to weapons-grade levels.
The report came as Stephen Bosworth, a senior US state department official responsible for North Korea, was travelling to Asia to try to revive six-party talks on Pyongyang's nuclear programme.
Beginning with a stop in the South Korean capital Seoul, Mr Bosworth will then travel to Tokyo and Beijing.
North Korea has nuclear and missile programmes and conducted underground atomic tests in 2006 and 2009.
The speed with which the country is pressing ahead with its nuclear programme will deepen suspicions that it is receiving help from abroad in circumventing United Nations sanctions, correspondents say.
Multinational talks on how to end the North's nuclear programme stalled when tensions rose over the alleged North Korean sinking of a South Korean warship in March, in which 46 South Korean sailors died.
The North has reportedly expressed a conditional willingness to return to talks and some analysts suggest it may have revealed these new uranium enrichment facilities in a bid to strengthen its negotiating hand.