Gen. Jeong Kyeong-doo, chairman of South Korea's Joint Chiefs of Staff, and his American counterpart Gen. Joseph Dunford agreed to take related measures at the earliest possible date, which apparently include the temporary dispatch of US strategic assets like long-range bombers to Korea.

Four F-15K fighter jets of South Korea conducted a live-bombing drill aimed at removing the North's leadership in case of an emergency situation, the Air Force said.

It's quite unusual for the secretive nation to fire a ballistic missile from its capital, another sign that it's diversifying launch areas to dodge external surveillance and a possible pre-emptive strike.