The governments of South Korea, the U.S. and Japan have all denied a Japanese media report of a second nuclear test by North Korea on Wednesday.

The three countries said they did not detect the seismic waves mentioned in the report.

A Seoul official questioned the report's accuracy citing no unusual moves by the North. He added that if there were a tremor, South Korea would have detected it.

Presidential spokesman Yoon Tae-young also said Seoul has detected nothing unusual while a Foreign Ministry official said a close watch on North Korea has found no intelligence on a second test.

Reuters quoted Japanese Prime Minister Shinzo Abe as denying evidence confirming a second test as well.

And a U.S. National Security Council spokesman said the Japanese report cannot be confirmed.

Meanwhile, the Korea Institute of Geoscience and Mineral Resources said the seismic wave may have been caused by a magnitude six quake in the waters off Japan's Fukushima Prefecture Wednesday morning.