North Korea is operating a secret underground plant to make nuclear bombs from highly enriched uranium (HEU) despite denying that such a programme exists, a South Korean newspaper said Wednesday.Dong-A Ilbo, quoting an unnamed senior government source, said South Korea and the United States have shared intelligence on the plant in Yongbyon district. Seoul's National Intelligence Service refused comment on the report. "Despite North Korea's denial that uranium enrichment programmes exist, South Korea and the United States have shared information that North Korea has built an uranium enrichment plant which is in operation," the source told Dong-A. Dong-A said both countries believe the facility can produce HEU for nuclear bombs. It said the plant is located at Sowi-ri in Yongbyon, North Pyongan Province, where the North's plutonium-based nuclear complex is situated. The source was quoted as declining to give further details such as the technological level and the output of highly enriched uranium. Washington's claims in 2002 of a secret HEU programme torpedoed the 1994 deal and sparked a new nuclear crisis. Pyongyang rejected the US allegations and restarted its reactor in protest.