North Korea fired a ballistic missile Wednesday, Seoul said, a week after Kim Jong Un vowed to boost Pyongyang's nuclear arsenal and just days before the South inaugurates a new, hawkish president.

North Korea fired the ballistic missile at 12:03 pm (0303 GMT), Seoul's Joint Chiefs of Staff said, likely from the Sunan Airfield near Pyongyang, the site of previous recent ICBM tests.

The missile flew 470 kilometers (300 miles) and reached an altitude of 780 kilometers, the JCS said, adding it was a "blatant violation of UN Security Council resolutions".

The Wednesday test comes days before the May 10 inauguration of South Korea's President-elect Yoon Suk-yeol, who has vowed to take a hard line with North Korea and ramp up security cooperation with the United States after years of failed diplomacy.

Japan's state minister of defence Makoto Oniki confirmed the launch and the missile's trajectory, saying it had landed "outside of Japan's exclusive economic zone".

North Korea's "repeated launches of ballistic missiles threaten peace and safety of our nation, the region and the international community," Oniki said.

North Korean leader Kim Jong Un has vowed to further strengthen the military
North Korean leader Kim Jong Un has vowed to further strengthen the military AFP / Jung Yeon-je

Pyongyang has conducted 14 weapons tests since January, including firing an intercontinental ballistic missile at full-range for the first time since 2017.

Last week, while overseeing a huge military parade, North Korean leader Kim vowed to develop his nuclear forces "at the fastest possible speed" and warned of possible "pre-emptive" strikes.

Meanwhile, satellite imagery indicates he may soon resume nuclear testing.

Analysts said Kim's messaging on his nuclear weapons, plus the recent test, could be seen as a signal to President-elect Yoon, who has threatened a pre-emptive strike on Pyongyang.

"It could be a warning message to... Yoon," said Hong Min of the Korea Institute for National Unification.

Yoon has suggested he is only willing to talk about peace if North Korea confirms it is willing to denuclearise -- something Pyongyang will never accept, Hong said.

Map showing the North Korea missile launch on Wednesday, May 4.
Map showing the North Korea missile launch on Wednesday, May 4. AFP / STAFF

Repeated negotiations aimed at convincing Kim to give up his nuclear weapons have come to nothing.

"We're still very concerned about these tests and the provocative nature of their ballistic missile program," said Pentagon spokesman John Kirby.

"We have called for the North to sit down again without precondition" to discuss denuclearisation.

"It's also why we continue to focus on the readiness of our alliance" with South Korea and Japan, Kirby said.

He noted that US Defense Secretary Lloyd Austin held a meeting at the Pentagon Wednesday with visiting Japanese Defence Minister Nobuo Kishi.

UN Secretary-General Antonio Guterres, meanwhile, urged North Korea "to fully comply with its international obligations", and said the newest launch "only contributes to increasing regional and international tensions", according to his spokesman Stephane Dujarric.

For five years under President Moon Jae-in, Seoul has pursued a policy of engagement with Pyongyang, brokering high-level summits between Kim and Trump while reducing joint US military drills the North sees as provocative.

But for President-elect Yoon, this "subservient" approach has been a manifest failure.

He said on the campaign trail he would like more US missile defences -- and even tactical nuclear weapons -- deployed in South Korea, and has vowed to ramp up joint military exercises, which infuriate Pyongyang.

US President Joe Biden is due to visit South Korea later this month to meet with Yoon.

Asked about a vote on a US draft resolution to increase international sanctions on Pyongyang, US Ambassador to the UN Linda Thomas-Greenfield said her country's plan was "to move forward with that resolution during this month".

However, it is "virtually impossible" for the Security Council to sanction North Korea -- which has supported Russia's attack on Ukraine -- due to Moscow's veto power, said Cheong Seong-chang of the Center for North Korea Studies at the Sejong Institute.

"The North therefore will try to test as many missiles as possible that it has not been able to do so far, enabling it to enhance capabilities of its arsenal at a fast pace."