North Korea has fired a ballistic missile, South Korea’s military chiefs say.
South Korea’s military said it had responded with a “precision strike” missile exercise.
The US Pentagon said it was still assessing the “probable” launch, which happened at approximately 03:30 local time (18:30 GMT).
South Korean news agency Yonhap reported that the missile flew eastward from Pyongsong, South Pyongan province.
It is not clear how far it went or whether it flew over Japan as other missiles did earlier this year.
North Korea has test fired several other missiles this year, including its first intercontinental ballistic missiles, as tensions increase over its nuclear programme.
North Korea is thought to be focusing efforts on building long-range missiles with the potential of reaching the mainland continental US.
Pyongyang officials said the first of the longer-range missiles it tested in July could hit “any part of the world”, but the US military called it an intermediate-range missile instead.