A report says, North Korea is forging ahead with enriching uranium for nuclear weapons. This could add to its atomic arsenal and raise the risk it will sell nuclear know-how abroad.The report published by the Institute for Science and International Security came after warnings from South Korea that the North's nuclear threat has progressed at a rapid pace and reached a very alarming level. South Korea also said this week that the North is restoring facilities at its Yongbyon nuclear reactor, the source of weapons-grade plutonium in the past. The report, based on procurement data obtained by governments and information from Pakistan, said the uranium programme's status and location of the plants were unclear.