Kim Jong Un labeled South Korea his country's principal enemy
North Korean leader Kim Jong Un (C) labeled South Korea his country's 'principal enemy' while on a tour of a major munitions factory. AFP

North Korea's Kim Jong Un branded South Korea his country's "principal enemy" and warned he would not hesitate to annihilate it as he toured major weapons factories, state media said Wednesday.

The report follows recent live-fire exercises by Pyongyang's military near the contested maritime border that prompted counter-drills and evacuation orders for residents on two South Korean border islands.

Images in state media showed Kim, in a full-length black leather jacket, standing in front of what analysts said were short-range ballistic missile launchers, purportedly nuclear-capable.

"The historic time has come at last when we should define as a state most hostile toward the Democratic People's Republic of Korea the entity called the Republic of Korea (South Korea)," Kim was reported as saying by the official Korean Central News Agency.

Kim, urging factory workers to modernise and "produce more weapons", said he had "no intention of avoiding a war" and warned he would have no hesitation in "annihilating" South Korea, KCNA added.

News of the factory tour came a day after nearly 50 countries joined the United States in condemning North Korea's alleged transfers of weapons to Russia for use in Ukraine, which would violate rafts of United Nations sanctions.

The White House last week accused the North of sending both missiles and launchers to Russia in what it called a "significant and concerning escalation" of its support for Moscow's war effort.

The live-fire drills that started last Friday marked one of the most serious escalations between the two sides since 2010, when the North shelled Yeonpyeong island, leaving four dead, including two marines.

Kim, accompanied by senior party and military officials, toured multiple munitions factories on Monday and Tuesday, KCNA said, describing the visits as encouragement "in the struggle for attaining the huge production goal for the new year".

Kim said that while the North would not "unilaterally" trigger a confrontation, it had "no intention of avoiding a war".

Were Seoul to use force against the North, "we will have no hesitation in annihilating the ROK by mobilising all means and forces in our hands," KCNA reported Kim as saying.

Those comments signal a shift in North Korean policy and hint that Pyongyang will take a "much tougher stance" toward Seoul in future, Hong Min, of the Korea Institute for National Unification, told AFP.

"It is the first time that the North has called the South its 'principle enemy', signifying the change of North Korea's Seoul approach to an ultra-hawkish mode," he said.

The North's recent artillery drills were "emblematic of the changed approach," he added.

Relations between the two Koreas are at one of their lowest points in decades, after Kim enshrined the country's status as a nuclear power into the constitution and test-fired several advanced intercontinental ballistic missiles.

At Pyongyang's year-end policy meetings, Kim threatened a nuclear attack on the South and called for a build-up of his country's military arsenal ahead of armed conflict that he warned could "break out any time".

Kim also successfully put a spy satellite into orbit late last year, after receiving what Seoul said was Russian help, in exchange for arms transfers for Moscow's war in Ukraine.