South Korea says North's nuclear capability 'speeding up', calls for action

By Jack Kim SEOUL (Reuters) - South Korea's foreign minister said on Saturday that North Korea's nuclear capability is expanding fast, echoing alarm around the world over the isolated state's fifth nuclear test carried out in defiance of U.N. sanctions. North Korea conducted its biggest nuclear test on Friday and said it had mastered the ability to mount a warhead on a ballistic missile, ratcheting up a threat that rivals and the United Nations have been powerless to contain. The test proved Nor