"North Korea fires unidentified ballistic missile towards East Sea," Seoul's Joint Chiefs of Staff said in a statement, referring to the body of water also known as the Sea of Japan.

The Joint Chiefs of Staff said had it detected the launch but gave no further details.

Japan's coast guard said that an "object, potentially ballistic missile, launched from North Korea," citing information from the country's defence ministry, and warning vessels to take care.

North Korea's last missile test was of a Hwasong-18 solid-fuel intercontinental ballistic missile, which it fired into the East Sea on December 18.

The apparent test comes days after North Korea conducted a series of rare live-fire drills near the maritime border with the South, prompting counter-exercises and evacuation orders for some South Korean border islands.

Leader Kim Jong Un also earlier this week branded Seoul his "principal enemy" and warned he would not hesitate to annihilate the South, as he toured major weapons factories.

"The historic time has come at last when we should define as a state most hostile toward the Democratic People's Republic of Korea the entity called the Republic of Korea (South Korea)," Kim was reported Wednesday as saying by the official Korean Central News Agency.

Analysts said at the time that the shift was significant, signifying a shift in Pyongyang's approach to Seoul into "ultra-hawkish mode".

- Ties woeful -

Relations between the two Koreas are at one of their lowest points in decades, after Kim enshrined the country's permanent status as a nuclear power into the constitution and test-fired several advanced intercontinental ballistic missiles.

Last year, Pyongyang also successfully put a reconnaissance satellite into orbit, after receiving what South Korea claimed was Russian assistance, in exchange for arms shipments for Moscow's war in Ukraine.

Kim has also test-fired a string of advanced intercontinental ballistic missiles (ICBMs) including a purported solid fuel version.

At Pyongyang's year-end policy meetings, Kim threatened a nuclear attack on the South and called for a build-up of his country's military arsenal ahead of armed conflict that he warned could "break out any time".

Pyongyang declared itself an "irreversible" nuclear power in 2022 and has repeatedly said it will never give up its nuclear weapons programme, which the regime views as essential for its survival.

The United Nations Security Council has adopted many resolutions calling on North Korea to halt its nuclear and ballistic missile programmes since Pyongyang first conducted a nuclear test in 2006.