The Democratic People's Republic of Korea (DPRK) on Saturday denounced South Korea's claim of the Northern Limit Line (NLL) along their disputed western sea border as invasion of its territory, the official news agency KCNA reported.

The South Korean political groups' insistence on the NLL is just sophism to justify their infringement upon the DPRK's sovereignty and invasion of its territory, and acts of aggression to hurt its national defense and security, said a spokesman for the Policy Department of the National Defense Commission of the DPRK.

"The call for preserving the NLL can only be construed as a declaration of confrontation and only cause the repetition of the Yonphyong Island shelling incident," the KCNA quoted the spokesman as saying.

South Korea's Navy on Sept. 21 fired warning shots at six DPRK's fishing boats, which the DPRK has asserted as peaceful fishing boats of some other country.

The DPRK refuses to acknowledge the NLL, which was drawn unilaterally by the U.S.-led UN Command at the end of the 1950-53 Korean War. The disputed demarcation line has long been a crucial element that triggers tensions between the two sides.

The DPRK and South Korea exchanged fire in the disputed waters in November 2010, killing at least two South Korean marines and injuring 16 others.

According to the KCNA report, the Southwest Front Command of the Korean People's Army (KPA) was ordered to stand ready to fight a "great war of national unification" if South Korea fires "even a bullet" into the DPRK's territory.?