The latest launch came after North Korean leader Kim Jong-un vowed to further boost the country's military capability at a high-profile ruling party conference last week.
North Korea has fired what appeared to be a ballistic missile into the sea, in the first such launch by Pyongyang this year.
The South Korean military said on Wednesday the North fired what is "presumed to be a ballistic missile" towards the sea east of the peninsula at around 2310 GMT (8:10 am) on Tuesday.
After an emergency meeting, South Korea's national security council "expressed concerns over the launch", according to a statement by the president's office.
Japanese Prime Minister Fumio Kishida described it as a "possible ballistic missile launch".
"There have been no reports of damage to Japanese aircraft and vessels so far," Japan's top government spokesman Hirokazu Matsuno told reporters.
"We are continuing analysis, but if it took a normal orbit, it is expected to have travelled about 500 kilometres and fallen outside Japan’s exclusive economic zone."
First missile launch of 2022
In the decade since Kim Jong-un took power, North Korea has seen rapid progress in its military technology at the cost of international sanctions.
The nuclear-armed nation's first apparent weapons launch of 2022 followed a year of major arms tests despite the severe economic hardship during the coronavirus pandemic.
The launch followed a speech by Kim last week in which he said North Korea would continue to build up its military capabilities.
In 2021, North Korea said it successfully tested a new type of submarine-launched ballistic missile, a long-range cruise missile, a train-launched weapon, and what it described as a hypersonic warhead.
The dialogue between Washington and Pyongyang remains stalled, following the collapse of talks between Kim and then-president Donald Trump in 2019.
Under Trump's successor Joe Biden, the United States has repeatedly declared its willingness to meet North Korean representatives, while saying it will seek denuclearisation.
But Pyongyang has so far dismissed the offer, accusing Washington of pursuing "hostile" policies.
However, South Korean President Moon Jae-in said on Wednesday that he will not give up hope for dialogue with Pyongyang despite the launch, his office said.