South Korean media: Seoul's military believes North Korea readying ballistic missile

NORTH KOREA -- South Korean media says Seoul's military believes North Korea is readying the launch of a ballistic missile, possibly an ICBM.

Yonhap news agency reports that Seoul's defense ministry also measures North Korea's nuclear test at 50 kilotons. The detonation Sunday was the strongest ever from the North, which claimed the test was of a hydrogen bomb.

South Korea responded to the nuclear test with live-fire drills off its eastern coast Monday that were meant to simulate an attack on the North's main nuclear test site.