Details of the launch were being analyzed by South Korean and US intelligence authorities, Reuters reported citing South Korea's Joint Chiefs of Staff statement on Saturday.
It was the latest in a series of missile tests and military exercises conducted by the North in recent weeks.
Seoul announced sanctions on Friday on five North Korean individuals and one company in response to Pyongyang's launch of what it said was a space rocket last month.
On Thursday state media KCNA reported that Pyongyang had conducted a simulated "scorched-earth" nuclear strike on targets across South Korea, drawing criticism from Seoul.
The joint annual summertime exercises between South Korea and the US known as the Ulchi Freedom Shield came to a close on Thursday after an 11-day run featuring air drills with B-1B bombers.
North Korea protested the deployment of the US strategic bombers by firing two ballistic missiles just hours later in retaliation.
Pyongyang has long denounced the drills as a rehearsal for war.
AMK/PR