North Korea has fired what could be a ballistic missile, Japan's coast guard says, in what would be the first test since the nuclear-armed country conducted a record number of launches in January.
South Korea's Joint Chiefs of Staff also reported North Korea had fired at least one "unidentified projectile" eastward.
Sunday's launch came less than two weeks ahead of a pivotal March 9 presidential election in South Korea, amid fears by some in Seoul that North Korea may push ahead with missile development while international attention is focused on Russia's invasion of Ukraine.
The leading conservative candidate, Yoon Suk-Yeol, warned last week 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 US 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's last test was on January 30, when it fired a Hwasong-12 intermediate range ballistic missile, the largest weapon fired since 2017. That capped a record month of mostly short-range missile launches in January.
North Korea, which has close ties to China, did not test any missiles during the Beijing Olympics in February.
The 2022 Winter Paralympics are due to begin in Beijing on March 4.
Complaining of unrelenting "hostile policies" from the US, North Korea has suggested it could resume testing its longer-range missiles or even nuclear weapons.
There was no immediate comment from the Pentagon or the US 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 UN Security Council resolutions, which have imposed sanctions on the country over its missile and nuclear weapons programs.