South Korea's Joint Chiefs of Staff reported that North Korea had fired one suspected ballistic missile toward the sea off its east coast from a location near Sunan, where Pyongyang's international airport is located.
The airport has been the site of missile tests, including a pair of short-range ballistic missiles fired on Jan 16.
Japan's Defense Minister Nobuo Kishi said Sunday's missile may have flown as high as 600 km (400 miles), to a range of 300 km (200 miles).
"There have been frequent launches since the start of the year, and North Korea is continuing to rapidly develop ballistic missile technology," Kishi said in a televised statement. North Korea was threatening the security of Japan, the region and the international community, he said.
North Korea's last test was on Jan 30, when it fired a Hwasong-12 intermediate range ballistic missile.
The largest weapon test-fired since 2017, the Hwasong-12 was reported to have flown to an altitude of about 2,000 km (1,200 miles) and range of 800 km (500 miles). That capped a record month of mostly short-range missile launches in January.
LAUNCH AMID S KOREA ELECTION, 'PUTIN'S WAR'
Sunday's launch came less than two weeks ahead of South Korea's March 9 presidential election, amid fears by some in Seoul and Tokyo that Pyongyang may push ahead with missile development while international attention is focused on Russia's invasion of Ukraine.
This launch comes as the international community is responding to the Russian invasion of Ukraine, and if North Korea is making use of that situation, it is something we cannot tolerate," Kishi said.
South Korea's National Security Council convened an emergency meeting to discuss the launch, which it called "regrettable," according to a statement from the presidential Blue House.
"Launching a ballistic missile at a time when the world is making efforts to resolve the Ukraine war is never desirable for peace and stability in the world, the region, and on the Korean Peninsula," the statement said.
The leading conservative candidate, Yoon Suk-Yeol, warned last week that North Korea could see the Ukraine crisis as "an opportunity for launching its own provocation."
Candidates and analysts have noted, however, that even before the invasion North Korean leader Kim Jong Un was overseeing an increase in missile tests as talks with the United States and its allies remain stalled.
"Putin’s War shapes almost all geopolitics right now, and should factor somewhere in Kim’s calculus — but even 'taking advantage of distraction' seems to presume too much, since (North Korea) was already testing aggressively before the war," John Delury, a professor at South Korea's Yonsei University, said on Twitter.
North Korea, which has close ties to China, did not test any missiles during the Beijing Olympics in February. The 2022 Winter Paralympics begin in Beijing on Friday.
Complaining of unrelenting "hostile policies" from the United States, North Korea has suggested it could resume testing its longer-range missiles or even nuclear weapons.
Pyongyang has an ambitious schedule of military modernisation, and the Kim regime’s strength and legitimacy have become tied to testing ever-better missiles, said Leif-Eric Easley, a professor at Ewha University in Seoul.
"North Korea is not going to do anyone the favour of staying quiet while the world deals with Russia’s aggression against Ukraine," he said.
There was no immediate comment from the Pentagon or the U.S. State Department on Sunday's launch. Washington says it is open to talks with North Korea without preconditions, but Pyongyang has so far rejected those overtures as insincere.
North Korea's ballistic missile launches are banned by United Nations Security Council resolutions, which have imposed sanctions on the country over its missile and nuclear weapons programmes.
In its first comments since Russia's Thursday invasion of Ukraine, North Korea's foreign ministry on Saturday posted a statement by a researcher who called the United States the "root cause" of the crisis for pursuing unilateral sanctions and pressure while disregarding Russia's legitimate demands for its security.