South Korea has said that North Korea had fired multiple ballistic missiles into the Sea of Japan.
"Our military detected around 09:20 (0020 GMT) several ballistic missiles launched from the Pyongyang area towards the East Sea," the Joint Chiefs of Staff said in a statement, referring to the Sea of Japan.
"Our military has stepped up surveillance and vigilance against possible additional launches," it added.
The launch follows Pyongyang's test-firing of a ballistic missile earlier this month that it said incorporated artificial intelligence technology.
That missile, fired on October 3, "is capable of changing its flight orbit at a low altitude and AI was introduced into it", Kim Yo Jong, the powerful sister of North Korean leader Kim Jong Un, said at the time.
Seoul days later announced the successful test of its first homegrown hypersonic glide vehicle (HGV), a weapon carried into the upper atmosphere by rocket boosters or ballistic missiles before gliding towards their targets.
South Korea's presidential office said the HGV offered "a new deterrence capability capable of striking key targets within the Korean Peninsula's operational environment".
Tensions between the two Koreas have been heightened since three South Korean soldiers were injured when two landmines detonated in the Seoul-controlled area of the Demilitarised Zone (DMZ) that has served as a buffer since the 1953 armistice.
A joint Seoul-UN investigation alleged that North Korea had planted the landmines over a year ago, something Pyongyang has angrily denied.
