The United States has scrambled to reinforce its Pacific missile defences as North Korea pushed more global alarm buttons yesterday by announcing it had authorised plans for possible nuclear strikes on US targets.
US Defence Secretary Chuck Hagel said Pyongyang's increasingly bellicose threats combined with its military capabilities represented a "real and clear danger" to the United States and its allies South Korea and Japan.
The Pentagon said it would send ground-based THAAD missile-interceptor batteries to protect bases on Guam, a US territory some 3,380 kilometres southeast of North Korea.
Shortly afterwards, the North Korean military said it had received final approval for military action against the US, possibly involving nuclear weapons.
While few of the North's threats have been matched with action, South Korea said it appeared to have moved a medium-range missile to its east coast. South Korean Defence Minister Kim Kwan-jin said he did not know the reasons behind the North's missile move, and that it "could be for testing or drills".
He dismissed reports that the missile could be a KN-08, which is believed to be a long-range missile that if operable could hit the US. The missile had "considerable range" but not enough to hit the US mainland, he said.
The new nuclear threats drew fresh concern led by UN chief Ban Ki-moon, who said he was "deeply concerned and troubled" over the escalating rhetoric. "At this time, I think all the parties concerned in the Korean peninsula, in particular the Chinese government, can play a very important role to calm down the situation," Ban said.
The European Union also called on North Korea to stop stoking tensions and re-engage with the international community. Russia termed the North's neglect of UN resolutions as "categorically unacceptable".
North Korea blocked access to its Kaesong joint industrial zone with South Korea yesterday for the second day running, and threatened to pull out its 53,000 workers in reaction to the South's airing of a "military" contingency plan to protect its own workers.
The North says the South Koreans in Kaesong can leave whenever they want. About 200 left yesterday but some 600 remain to keep the factories running.
Additional reporting by Associated Press