North Korea fires a ballistic missile into sea, South Korea says

The firing comes after North Korea threatened on Friday an "unprecedentedly persistent, strong" response as South Korea and the United States gear up for annual military exercises as part of efforts to fend off the North's growing nuclear and missile threats.

North Korea fired a ballistic missile toward the sea off its east coast on Saturday, South Korea's Joint Chiefs of Staff said.

This photo provided by the North Korean government, shows what it says is Hwasong-17 intercontinental ballistic missiles during a military parade to mark the 75th founding anniversary of the Korean People's Army on Kim Il Sung Square in Pyongyang. (AP/ Representative Image)

Japan's Coast Guard also said North Korea fired what could be a ballistic missile.

The firing comes after North Korea threatened on Friday an "unprecedentedly persistent, strong" response as South Korea and the United States gear up for annual military exercises as part of efforts to fend off the North's growing nuclear and missile threats. (ALSO READ: North Korea bans girls from having same name as Kim Jong Un's daughter: Report)

Pyongyang may have created a military unit tasked with operating new intercontinental ballistic missiles, in line with its recent restructuring of the military, state media video footage from a February 9 parade suggested.