SEOUL, Nov. 30 (Yonhap) -- North Korea vowed Tuesday to step up its uranium enrichment activities for "peaceful purposes" and claimed that it has thousands of centrifuges, deepening outside worries that they could be used as a second means of building nuclear bombs.

   The announcement is hardly a surprise as Pyongyang has already made the same claim to a visiting U.S. expert recently. But it comes as tension soars to the highest point in years on the Korean Peninsula after the communist state shelled a South Korean island last Tuesday and killed four people, including two civilians.

   South Korea and the United States have been engaged in a massive naval exercise since Sunday in a show of force against North Korea, mobilizing a supercarrier and drawing threats of retaliation from Pyongyang if the disputed Yellow Sea border is violated.

   "Currently, the construction of a light-water reactor is actively underway," said the Rodong Sinmun, the paper of the North's ruling Workers' Party, referring to a nuclear facility that uses low-enriched uranium to produce energy.

   "To guarantee fuel for it, a uranium enrichment factory is operating, equipped with thousands of centrifuges," the paper said in the report carried by the North's official Korean Central News Agency. "To resolve energy needs, the nuclear energy development project for peace purposes will be pushed harder."

   Centrifuges, which a Stanford University professor, Siegfried Hecker, said the North operated from an "ultra-modern control room," can also be used to produce highly enriched uranium, an additional means of nuclear arms development for North Korea, which tested two plutonium-based bombs in 2006 and 2009.

   Uranium-based bombs pose a greater threat to non-proliferation efforts because their development process can be easily hidden while they are easier to transport, according to experts.

   North Korea told Hecker that it was enriching uranium to meet its peaceful energy needs, but senior U.S. officials, including Defense Secretary Robert Gates, have rejected the claim as false.

   samkim@yna.co.kr
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