The South Korean military says North Korea has fired two projectiles believed to be short-range ballistic missiles toward the sea off its east coast.
South Korea's Joint Chiefs of Staff made the announcement shortly after 8:00 a.m. on Thursday, local time.
It is working with US forces to gather and analyze information about the launch.
North Korea has repeatedly launched missiles since the beginning of this year.
It fired one projectile each on January 5 and 11, and announced the next day that it had tested a hypersonic missile.
It also fired two projectiles each on January 14 and 17. They are believed to have been short-range ballistic missiles.
On Tuesday, South Korean military sources said the North had fired what appeared to be two cruise missiles.
Thursday's launch, the sixth this year, underscores Pyongyang's intention to boost its military capabilities.
North Korea's ruling Workers' Party political bureau decided at a meeting on January 19 that the country must prepare for a long-term confrontation with US imperialism.
It hinted at reviewing its unilateral suspension of nuclear and intercontinental ballistic missile tests announced in 2018.
Observers say North Korea is sending a warning to the US, which unveiled new sanctions over Pyongyang's nuclear and missile tests and has called for the UN Security Council to issue a statement urging the North to abide by its resolutions.