At least two projectiles were launched from North Korea, the coast guard said, while Japan's public broadcaster NHK said the objects appears to have fallen outside Japan's exclusive economic zone.

"What appears to be a ballistic missile was launched from North Korea," the coast guard said in a statement issued at 6:47 am (2147 GMT).

In a second statement issued about 15 minutes later, the coast guard said another apparent ballistic missile was launched.

NHK said the both projectiles seemed to have fallen outside Japan's exclusive economic zones, citing government sources.

Nuclear-armed North Korea has carried out a record-breaking blitz of weapons tests this year, including two ballistic missiles launched on Thursday, just hours after US Vice President Kamala Harris left South Korea.

South Korean and US officials have also been warning for months that North Korean leader Kim Jong Un is preparing to conduct another nuclear test.

North Korea, which is under multiple UN sanctions for its weapons programmes, typically seeks to maximise the geopolitical impact of its tests with careful timing.