South Korea's Joint Chief of Staff said early on Wednesday that North Korea fired three missiles toward waters off North Korea's eastern coast, one after another, between 6 and 7 a.m. local time.
Japan's Coast Guard also reported at least two projectiles believed to be ballistic missiles falling into the sea.
South Korea's military said the projectiles hailed from the Sunan area in Pyongyang.
North Korea has been testing weapons at an unprecedented pace in 2022, including the country's first demonstration of an intercontinental ballistic missile in March. Wednesday's apparent tests would be the 17th of the year.
UN resolutions prohibit North Korea from testing missiles capable of carrying a nuclear warhead.
The launch comes soon after US President Joe Biden's five-day tour of the region, starting in South Korea and moving on to Japan, which concluded with Tuesday's Quad meeting with the leaders of Japan, India and Australia.
US condemns 'destabilizing' missile tests
US national security adviser Jake Sullivan addressed the issue in a call with his South Korean counterpart Kim Sung-han on Tuesday.
"They both condemned the DPRK's destabilizing ballistic missile tests and committed to continue building on their close coordination. Mr. Sullivan also reaffirmed the United States' steadfast commitment to the defense of the ROK," the White House said in a statement.
The White House had previously said that there was a "genuine possibility" that Pyongyang would carry out a missile test around the time of Biden's Asia trip.
The US has also recently warned that North Korea might be preparing another nuclear test, having last carried one out in 2017 before declaring a self-imposed moratorium on future tests amid attempts at diplomacy with former President Donald Trump.
North Korea also battling COVID outbreak
The apparent tests also coincide with North Korea's first acknowledged COVID outbreak. The reclusive country locked down its borders with China in response to the outbreak in 2020 and had claimed not to have any known cases until recently.
Details on the possible outbreak have been extremely vague. With testing facilities almost non-existent, the country's state media had only been reporting supposed cases of people having a fever.
On Wednesday, state news agency KCNA claimed that the measures the country had taken had had "successes" and were "maintaining the clearly stable situation." KCNA reported that almost 116,000 people showed fever symptoms on Wednesday, down roughly 18,000 on the previous day. No new deaths were reported by the state's emergency epidemic prevention headquarters, it said.
North Korea has claimed just over 3 million cases of feverishness but only 68 deaths to date.
After initial days where state media reports suggested an angry Kim Jong Un calling in the army to help and sacking responsible officials, it has since moved its focus to "an all-out scientific and lightning anti-epidemic campaign," which it claims is having positive effects.
"Gaining momentum is the work to consolidate the anti-epidemic foundations of the country and apply the most excellent and suitable treatment tactics and methods across the country," KCNA wrote, without elaborating.
