N. Korea carries out apparent nuclear test North Korea has pulled manpower and equipment out of its nuclear test site, a report says. NORTH Korea has staged an apparent nuclear test in a striking act of defiance that, if confirmed, is sure to trigger global condemnation from enemies and allies alike. Regional seismic monitoring agencies detected a seismic event, of a magnitude between 4.9 and 5.1, at 11.57am (1357 AEDT) on Tuesday with the epicentre in the same location as the North's Punggye-ri nuclear test site. "At this point, the seismic activity ... appears to indicate a nuclear test by North Korea," the South's Yonhap news agency cited an unidentified foreign ministry official as saying. The US Geological Survey noted the tremor had a very shallow depth of just one kilometre. The South Korean defence ministry and the presidential Blue House both said they were trying to verify whether a nuclear detonation had taken place. Pyongyang has been threatening a nuclear test for weeks despite warnings of severe repercussions from the UN Security Council. If confirmed, it would mark the third time the North has detonated a nuclear device, following previous tests in 2006 and 2009. It would throw down a stark security and diplomatic challenge to US President Barack Obama at the start of his second term, and to regional neighbours China, Japan and South Korea, all of which have new or incoming leaders. The first priority for the international community will be determining the precise nature and yield of any test and what it reveals about the technical level of the North's nuclear weapons program. Pyongyang's promise of a "higher level" test had fuelled speculation it would be of a uranium device, compared to the plutonium ones detonated in 2006 and 2009. A uranium test would confirm suspicions that the North has been secretly enriching weapons-grade uranium for years and would open a path for Pyongyang to significantly expand its small nuclear arsenal. There will be particular concern at any sign that the North has made progress in the technically complex process of "miniaturising" a bomb to fit on the head of a long-range missile. Pyongyang had announced its nuclear test plan as a defiant response to a UN Security Council resolution that condemned the launch as a disguised ballistic missile experiment and tightened sanctions.