The unification ministry on Wednesday slammed North Korean leader Kim Jong-un's recent reference to South Korea as the "principal enemy" of the regime.

In a statement, the ministry said Kim continued to reveal his ambition to unify the Korean Peninsula by force with mentions of "war" during visits to major munitions factories this week.

It went on to say that North Korea has persistently attempted to ratchet up military tensions on the peninsula, including threats of armed provocations, since the beginning of the year while instilling hostility among its people toward South Korea.

The unification ministry called such moves an "old-fashioned tactic" to try to shake up South Korean society, adding they show how Pyongyang is fearful of and anxious about Seoul and Washington's reinforcement of extended deterrence.

It urged Pyongyang to immediately stop its reckless military threats and psychological warfare against Seoul, adding that the latter will respond resolutely to any provocation and consistently pursue normalization of inter-Korean relations based on principles.