North Korea fired a short-range ballistic missile on Sunday, Seoul's military said, the fourth show of force in a week as South Korea and the United States stage major military drills.
Seoul and Washington have ramped up defence cooperation in the face of growing military and nuclear threats from the North, which has conducted a series of increasingly provocative banned weapons tests in recent months.
South Korea and the United States are currently in the middle of 11 days of joint drills known as Freedom Shield, their largest in five years.