The North has stoked international alarm over its banned nuclear missile programme but before Wednesday had not staged a missile test since September 15, raising hopes that ramped-up sanctions were having an impact.
The missile flew east from South Pyongan Province, the military Joint Chiefs of Staff (JCS) said.
The US Pentagon said it had detected a "probable missile launch" from North Korea.
South Korea's military staged a "precision strike" missile exercise in response, Yonhap news agency said, also quoting the JCS.
Seoul's unification minister had on Tuesday said signs of unusual activity had been detected in North Korea, hinting at a possible missile test.
The US last week unveiled new sanctions targeting North Korean shipping, raising pressure on Pyongyang to abandon it's atomic weapons programme.
Pyongyang condemned the move as a "serious provocation" and warned that sanctions would never succeed.
In September the North conducted its sixth and most powerful nuclear test and staged an intermediate-range missile launch over Japan.
Eyewitness? Submit your stories now via social or:
Email: eyewitness@pulse.ng
![Russian Deputy Defence Minister, Timur Ivanov [PhotoNews Pakistan]](data:image/svg+xml;charset=utf8,%3Csvg%20xmlns%3D'http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg'%20width%3D'300'%20height%3D'172'%20data-ring-placeholder%3D'1'%3E%3C%2Fsvg%3E "Russian Deputy Defence Minister, Timur Ivanov [PhotoNews Pakistan]")
