The launch comes days after North Korea tested an intercontinental ballistic missile in the Sea of Japan.
North Korea fired a ballistic missile into the sea off the east coast of the Korean peninsula, the Yonhap news agency reported, citing South Korea’s Joint Chiefs of Staff (JCS).
The JSC did not immediately provide details about Sunday’s launch.
The Japan Coast Guard also said that what was fired by North Korea could be a ballistic missile.
Launch comes after North Korea fired a suspected intercontinental ballistic missile (ICBM) in the sea between the Korean peninsula and Japan on Thursday, hours before the South Korean president flew to Tokyo for a summit who discussed ways to counter their neighbor with nuclear weapons.
North Korean state media described the launch of the Hwasong 17 as a response to the continuous and “frantic” joint drills by South Korea and the United States.
Seoul and Washington have stepped up security cooperation after a year of record-breaking weapons tests and nuclear threats from North Korea.
Pyongyang sees all these exercises as rehearsals for an invasion.
Last year, North Korea declared itself an “irreversible” nuclear power, and leader Kim Jong Un recently called for an “exponential” increase in weapons production, including tactical nuclear weapons.