Nuclear-armed North Korea test fired two strategic cruise missiles from a submarine on Sunday, state-run television KRT said just as US-South Korea military drills were due to begin.
KRT published five photos of the missile launched from a submarine on Monday. The photos showed that North Korea's submarine units were testing underwater offensive operations, confirming the reliability of the launch in the fog.
South Korean Chiefs of Staff said they would work with their US counterparts on the incident to analyze the details of the launch. The army was on high alert.
On Monday, South Korean and American troops were scheduled to begin 11 days of joint drills, dubbed "Freedom Shield 23," which will be held on a scale not seen since 2017. North Korea has long bristled over drills they regard as a rehearsal for invasion.