The drills on Tuesday came a day after South Korea and Japan reported North Korea's launch of several short-range ballistic missiles into the sea, its first such missile test in about two months.
Kim guided the drills on Monday that were aimed at testing the "real war capabilities" of 600mm multiple rocket launchers and improving the operators' combat morale and readiness posture, KCNA said.
The drills also included simulating an air explosion of a shell of the super-large multiple rocket launcher at a preset altitude above the target, it said.
The unit displayed "high mobility and accurate and strong striking power" in carrying out a sudden combat mission, eliciting the young leader's praise, it said.
"They fully demonstrated their excellent crack-shot artillery marksmanship and prompt and thorough combat readiness," KCNA said.
Kim called for modernising and scaling up artillery forces, highlighting the 600mm rocket launchers' "strategic duties as the core central striking means" in war preparations.
"The destructive offensive means possessed by our army should more thoroughly fulfil their missions to block and suppress the possibility of war with the constant perfect preparedness to collapse the capital of the enemy and the structure of its military forces," Kim told the troops, according to KCNA.
Pyongyang has broken with decades of its inter-Korean policy, scrapping a military pact and declaring the South a hostile enemy state.
When asked about threats by the North's multiple rocket launchers at a news conference on Monday, Seoul's defence minister, Shin Won-sik, said if Pyongyang fires a large number of conventional missiles against the South, it would "constitute a war" and prompt strong retaliatory attacks.
