On a tour of weapons factories, Mr Kim says the country needs "overwhelming military power" and calls on suppliers to ramp up production of missiles and rocket launchers for frontline artillery units.
North Korean leader Kim Jong Un says he wants his army to have the power to "surely annihilate" its enemies as he called on suppliers to deliver more missiles ahead of planned US-South Korea military exercises.
His country needs to have "overwhelming" force and be ready for war, he said, according to North Korean state media.
Mr Kim toured factories producing tactical missiles, missile launch platforms, armoured vehicles and artillery shells on Friday and Saturday, KCNA said.
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At a missile factory, he called on suppliers to "drastically boost" capacity to allow missiles to be mass produced for the frontline military units, KCNA said.
The demand to ramp up production of key arms comes ahead of the US and South Korea's joint summer military drills, scheduled to start in a week, which Mr Kim sees as a dry-run for invading his country.
The allies say they have no intention of attacking North Korea.
Mr Kim was quoted as saying: "The qualitative levels of war preparations depend on the development of the munitions industry, and the factory has a tremendous responsibility in accelerating our military's war preparations.
Mr Kim highlighted the "very urgent need" to "exponentially increase" production of large-calibre multiple rockets, KCNA said.
He said: "Our army must thoroughly secure overwhelming military power and solid readiness to handle any war at any time, so that the enemy does not dare to use force, and would be annihilated if it does."