North Korea fires over 20 missiles in a single day, prompting air raid warnings in South

North Korea has fired more than 20 missiles into the sea -- the highest number launched in a single day this year. One of these projectiles crossed the Northern Limit Line, a disputed inter-Korean maritime border. It is the first time one of Pyongyang's missiles have come so close to the South, prompting air raid warnings and retaliatory air-to-ground missiles. Seoul also closed some air routes off the east coast of the Korean Peninsula. South Korea said the series of launches marks the most aggressive provocation by the North in more than a decade.