Kim Jong-un convened an emergency meeting with top defense and security officials last Saturday and supposedly said: “The country will be under martial law starting from midnight on January 29, and all the frontline and central units should be ready for a war,” Korean Joongang Daily reported, citing an unidentified source.

The paper also speculated that the new nuclear test could be held either on February 16, the birthday of former leader Kim Jong-il, or February 25, the inauguration day of South Korean President-elect Park Geun-hye.

North Korea vowed on January 23 to strengthen its military capabilities and step up its controversial nuclear program shortly after the UN Security Council imposed new sanctions on the country over the December rocket launch.

Pyongyang also pledged to end any efforts at denuclearizing the Korean Peninsula and to withdraw from six-party talks.

Satellite images have shown that the reclusive communist regime has been digging a new underground tunnel at the Punggye-ri nuclear test site in the country's northeast, where it conducted two previous nuclear tests, first in 2006 and then in 2009.

North Korea has been subjected to several rounds of UN Security Council sanctions since it declared itself a nuclear power in 2005.