The presidential office of Cheong Wa Dae has denied foreign news reports that North Korea may have conducted a second nuclear test.

Presidential spokesman Yoon Tae-young said no seismic tremors were detected coming from North Korea, citing reports from the Korea Institute of Geoscience and Mineral Resources, a South Korean quake monitoring center.

Reuters news agency, Bloomberg news agency and Japan's Nihon TV reported earlier that North Korea conducted a second nuclear test Wednesday morning. The report said artificial seismic tremors indicating a nuclear detonation were detected at around 8:40 a.m.