The DPRK also refused to accept the inspection results by the International Atomic Energy Agency (IAEA) on the suspicious nuclear experiments in South Korea, and warned it won't give up its nuclear deterrent force until a "thorough and understandable" investigation is made.

"The DPRK can't recognize the results of three inspections made by the IAEA so far and will remain skeptical about the results of further inspections," the official Korean Central News Agency (KCNA)said in a commentary.

"The continued disclosure of nuclear-related secret experiments since September prove that south Korea has pursued a nuclear development program for the past more than two decades," said the commentary, adding that "it pose a grave threat to the peace on the Korean Peninsula and regional stability."

The commentary assailed the United States of applying double standards. "The US has manipulated the IAEA to drag on its inspection of nuclear research centers in south Korea...and the IAEA showed tendency to downplay the case," it said.

"It is the consistent stand of the DPRK to make the whole Korean Peninsula nuclear free,"it said.

"The DPRK can never dismantle its self-defensive nuclear deterrent force unless a thorough and understandable probe is made into south Korea's nuclear issue," warned the commentary.