North Korea Threatens U.S. With 'Powerful Nuclear Hammer'

North Korea threatened to launch a nuclear strike "at the heart of the U.S." if it sees signs that Washington is trying to remove Kim Jong Un as the country's leader, according to South Korea's Yonhap news agency.

"Should the U.S. dare to show even the slightest sign of attempt to remove our supreme leadership, we will strike a merciless blow at the heart of the U.S.