North Korean ruler Kim Jong Un has ordered personnel to "complete preparations for a nuclear test between Tuesday and yesterday" and for the detonation to take place in the near future, an anonymous source told the Korea JoongAng Daily on Thursday.
Kim also allegedly directed that "the country will be under martial law starting from midnight Jan. 29 and all the frontline and central units should be ready for a war," the source said.
International worries about a new North Korean nuclear test are at their highest point since the last detonation in spring 2009. Pyongyang has warned that an atomic blast is coming in response to the U.N. Security Council condemnation last week for the North's December launch of a long-range space rocket.
"This test could happen at any time without warning," according to the U.S. military command in South Korea. "A North Korean nuclear test would be a highly provocative act and a significant violation of United Nations Security Council resolutions."
Seoul has established an emergency response unit to search for signs of an atomic blast, according to a South Korean Defense Ministry spokesman.
The outgoing government of South Korean President Lee Myung-bak on Thursday called for Pyongyang "to immediately stop all acts and language of aggressive nature and abide by international obligations," Reuters reported.
"We warn that if the North ever makes a wrong judgment and again undertakes provocation, there will be grave consequences," a Lee spokesman said.
South Korean, U.S. and Japanese defense officials joined together on Thursday in releasing a combined statement that demands the North refrain from conducting its third nuclear test in less than a decade, the Xinhua News Agency reported.
Some U.S. intelligence insiders say the test could supply a first glimpse in nearly four years of any headway Pyongyang has made in creating a nuclear bomb that could target the United States and partnered nations, the New York Times reported.
The United States and others are looking to learn whether the North has acquired the ability to build highly enriched uranium-based bombs and whether it can make warheads compact enough to be mounted onto strategic ballistic missiles.
The North's two previous nuclear tests were only somewhat successful and nearly all of its long-range missile tests -- with the exception of the most recent space rocket launch in December -- have been failures.