North Korea leader Kim Jong-Un said in a New Year speech that he is ready for war if provoked by "invasive" outsiders.
In only his fourth speech since taking over from his father, he said: "If invasive outsiders and provocateurs touch us even slightly, we will not be forgiving in the least and sternly answer with a merciless, holy war of justice."
He called on his military to work on developing technologies with the aim of having more "diversified attack means".
But Kim also insisted he would pursue "unification" and added: "We will continue to work patiently to achieve peace on the Korean Peninsula and regional stability."
Laying the blame for frosty relations in the region firmly with the South, he said: "South Korea has made a unilateral case for unification and increased mistrust and conflict between us."
Yet he said he is open to talks with anyone interested in "reconciliation and peace" and promised to "aggressively" attempt to improve ties with the South.
Applause was played at various points throughout the apparently pre-recorded message.
Photographs of factories and farms were interspersed with footage of the North Korean leader standing in a wood-panelled room in front of a red flag bearing the crest of the ruling Workers' Party
Kim said in last year's address that he would be open to a summit with the South, but tensions increased in 2015, particularly in August, when a landmine blast on the border wounded two South Korean soldiers.
Seoul blamed Pyongyang, who denied responsibility.
The two sides met for talks after a military stand-off and agreed to reduce tensions and hold further discussions.
However, subsequent negotiations have been fruitless.
On Wednesday, North Korean state media said its top negotiator with the South, Kim Yang Gon, had been killed in a road accident.
"We should cherish last year's high-level talks and make continued efforts to seek dialogue and not take any further steps backwards," Kim said of the August talks.
In a response to the speech, South Korea's foreign ministry restated its position that it was open to talks, the Yonhap News Agency reported.
"North Korea should take note that we are seeking to develop inter-Korean relations and lay the groundwork for peaceful unification," an unnamed government official said.