"If North Korea goes ahead with a nuclear test, it will be a clear breach of the April 19 presidential statement by the U.N. Security Council and therefore the Security Council will have to take new actions," Foreign Ministry spokesman Sho Byung-jae said.
Yonhap News Agency reported officials believe the North is preparing to set off another nuclear device. The two previous rocket launches in 2006 and 2009 resulted in nuclear testing; however, there was no test after the failed April 13 launch.
The U.N. Security Council tightened sanctions against the North following the failed launch. It was condemned as a violation of U.N. resolutions that bar North Korea from testing ballistic missile technology.
If more tests are conducted, Sho warned it would "bring about grave consequences that do not help North Korea at all."