"North Korea fired an unidentified ballistic missile into East Sea," Seoul's Joint Chiefs of Staff said, referring to the body of water also known as the Sea of Japan. They did not give any further details.

Japan also confirmed the launch, telling residents of Hokkaido to "evacuate immediately" and seek shelter in a building or underground, warning the missile was expected to land around 8:00 am local time (2300 GMT).

Local government officials in Hokkaido later said there was "no possibility" of the missile hitting the island.

Pyongyang has opened the year with a flurry of weapons tests, including what its state media has claimed are nuclear-capable underwater drones and the launch of two intercontinental ballistic missiles.

North Korea has claimed to have conducted three tests of underwater drones -- known as Haeil, which means tsunami in Korean -- in less than three weeks so far.

Pyongyang has claimed the weapon is able to unleash a "radioactive tsunami".

- 'Escalating moves' -

On Monday, North Korean leader Kim Jong Un attended a meeting of the Central Military Commission to discuss ways to "cope with the escalating moves of the US imperialists and the south Korean puppet traitors to unleash a war of aggression," Pyongyang's Korean Central News Agency said.

Kim ordered that the country's deterrence capabilities be strengthened with "increasing speed" and in a "more practical and offensive" manner.

North Korea last year declared itself an "irreversible" nuclear power, effectively ending the possibility of denuclearisation talks.

Earlier this year, Kim ordered the military to intensify drills to prepare for a "real war".

In response, Washington and Seoul have intensified defence cooperation, staging joint military exercises with advanced stealth jets and high-profile US strategic assets.

North Korea views such exercises as rehearsals for invasion, and on Tuesday described them as "frantic" drills "simulating an all-out war against" Pyongyang.

South Korea on Tuesday also accused North Korea of being "irresponsible" after Pyongyang cut hotline contact with Seoul last week.

For five days, North Korea has not answered the twice-daily calls made through a military hotline and an inter-Korean liaison channel, South Korean Unification Minister Kwon Young-se told reporters.

The links were cut a day after Seoul accused Pyongyang of continued unauthorised use of a joint industrial complex in the North Korean city of Kaesong.

South Korea said North Korea had refused to accept its notice to cease activity at the factory, which was once a symbol of reconciliation.

Seoul pulled out of the venture in 2016 following a North Korean nuclear test, saying the complex was helping to fund Pyongyang's weapons programmes.