North Korea fired "multiple unidentified ballistic missiles" on Monday, South Korea's military said, the same day Seoul and Washington began a major annual joint military drill known as Freedom Shield.

North Korea on Monday condemned joint U.S.-South Korean military drills as a "provocative act," warning of the danger of sparking war with "an accidental single shot," days after Seoul's air force mistakenly bombed a village on its own territory.

The U.S. aircraft carrier USS Carl Vinson arrived at the southern port city of Busan in South Korea on Sunday as a show of force against North Korea, South Korea's navy said.