SEOUL - Seismic activity has been detected in?the Democratic People's Republic of Korea (DPRK) with an earthquake measuring 4.9 magnitude registered by the US Geological Survey, in a move that South Korea said indicated that Pyongyang had carried out a third nuclear test.

The quake occurred at 11:57 am Korean time (0257 GMT) and South Korea's presidential office said that it was "likely" a nuclear test, according to the South's Yonhap news agency

The DPRK?is not prone to seismic activity.

The USGS said the epicentre of the quake, which was only one km deep, was close to the North's known nuclear test site.

The DPRK, banned under United Nations Security Council resolutions from developing nuclear and missile technology, did not issue a statement and it was impossible to verify that it was a nuclear test.