Pyongyang is facing even tougher sanctions from the United Nations Security Council over last Friday`s test, the reclusive state`s most powerful to date.
Seoul`s defense ministry repeated its claim from last week that the North has an additional tunnel set up at its Punggye-ri site -- the location of all five tests since 2006.
Unification Minister Hong Yong-pyo also said Friday that "North Korea has been preparing a nuclear test and given the related developments, I think that it can do another nuclear test soon."
Meanwhile, the government is fending off a push by conservative lawmakers to deploy nuclear weapons in South Korea as a defensive measure.
President Park Geun-hye has already rejected the suggestion as contrary to the South`s own global obligations.
Prime Minister Hwang Kyo-ahn was quoted by local news agency Yonhap on Monday as demanding a "united" response within the South, leaning on any new UN sanctions.
Hwang said during a meeting that North Korea’s "fanatical development of nuclear arms and missiles would become the poison that would hasten the destruction of its regime rather than consolidate it”.
SKorea wary of 6th NKorean nuclear test
12 September 2016
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South Korea warned Monday that North Korea is in a position to carry out a sixth nuclear test -- just days after its latest atomic detonation.
