The news prompted a United Nations plea to North Korea to not to carry out the test. The confusion began after Unification Minister Ryoo Kihl-jae answered a lawmaker's question on increased personnel at the north's nuclear test site.
The U.N. said a test would be a "provocative" act amid soaring tensions on the Korean Peninsula.
A Unification Ministry official said that Ryoo had intended to say that North Korea has long been ready to conduct a nuclear test.
Meantime, North Korea said Monday it will withdraw thousands of its workers and suspend operations at the Kaesong industrial complex, which it has jointly run with South Korea. The announcement indicates North Korea is moving closer to severing its last economic link with its rival.
The statement comes amid weeks of North Korean war threats and other efforts to punish South Korea and the U.S. for ongoing joint military drills. North Korea is also angry over the U.S.-led push for U.N. sanctions.
The Associated Press contributed to this report.