The US is sending a missile shield to the Pacific island of Guam as North Korea threatens nuclear strikes. The Pentagon said the shield would be ready within weeks, adding to warships that were sent to the area earlier, Defense Secretary Chuck Hagel called a "real and clear danger" from Pyongyang. Hours later, South Korea's Yonhap news agency said North Korea had moved what appeared to be a mid-range Musudan missile to its east coast. It was not clear if the North planned to fire the rocket or was just putting it on display as a show of force, one South Korean government source was quoted as saying. North Korea also barred entry to a joint industrial complex it shares with the South for a second day on Thursday and said it would shut the zone if Seoul continued to insult it. Events on the Korean peninsula have begun to unnerve global financial markets long used to the rhetoric North Korea routinely hurls at Seoul and Washington. The North had named Guam among a list of possible targets for attack that included Hawaii and the US mainland.