It came after a US aircraft carrier arrived in South Korea to participate in joint drills, and ahead of a planned visit by Vice President Kamala Harris.

Seoul said the launch was an "act of grave provocation". The UN prohibits North Korea from ballistic and nuclear weapons tests.

South Korea's military said it detected a short range missile fired at just before 07:00 local time (11:00 GMT) close to Taechon, more than 100 km (60 miles) north of Pyongyang. It said it flew about 600 km at an altitude of 60 km.

"Our military maintains a full readiness posture and is closely cooperating with the US while strengthening surveillance and vigilance," it said in a statement.

Japan's coast guard confirmed the launch, warning ships to "be vigilant". Tokyo's defence minister Yasukazu Hamada said the missile reached a maximum altitude of around 50 km, falling in waters off North Korea's eastern coast, and outside Japan's exclusive economic zone.