N. Korea tests nuclear detonation device: Presidential office

North Korea has tested a nuclear detonation device apparently in preparation for its seventh nuclear test, a Presidential official said on Wednesday.

South Korea does not believe a nuclear test will happen in the next day or two, but it could "certainly" take place after that, Kim Tae-hyo, First Deputy Director of the National Security Office, told reporters.

North Korea is believed to be preparing for its first nuclear test in nearly five years at its Punggye-ri nuclear test site, Yonhap news agency reported.

Earlier on Wednesday, the country launched three ballistic missiles, including a presumed intercontinental ballistic missile.