North Korea has fired a submarine-launched ballistic missile into waters off the coast of Japan, South Korea's military has said.
Pyongyang unveiled the missile in January, describing it as "the world's most powerful weapon".
It comes weeks after South Korea unveiled a similar weapon of its own.
North Korea has carried out a flurry of missile tests in recent weeks, including of what it claimed were hypersonic and long-range weapons.
Some of these tests violate strict international sanctions.
The country is specifically prohibited by the United Nations from testing ballistic missiles as well as nuclear weapons.
The UN considers ballistic missiles to be more threatening than cruise missiles because they can carry more powerful payloads, have a longer range, and can fly faster.
On Tuesday South Korea's Joint Chiefs of Staff said one missile had been launched from the port of Sinpo, in the east of North Korea where Pyongyang usually bases its submarines. It landed in the East Sea, also known as the Sea of Japan.
South Korean media reported that this particular missile was believed to have travelled about 450km (280 miles) at a maximum height of 60km.
It is unclear if the missile was launched from a submarine or from an underwater platform.
Japan's Prime Minister Fumio Kishida said two ballistic missiles had been fired, calling the launches "very regrettable".
