The United States stations tens of thousands of US soldiers in South Korea, and the allies regularly stage joint drills, which they describe as defensive in nature.

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.