Kim's statement and the report of the drill came a day after North Korea fired what appeared to be two short-range missiles into the sea in the latest of a series of launches interspersed with spurned peace overtures to South Korea.
It came a week after the president of China, the North's only ally, visited the South in a trip seen as a pointed snub to Pyongyang, and as exposing a slow but steady shift in Cold War alliances in East Asia.
"We should be prepared for both words and actions," he was quoted as saying.
"However fair-minded and just we are, we may become a bargaining chip for the strong and our precious history inherited with blood will loose (sic) its shine in a moment if we are weak."
The KCNA report did not specify to whom Kim was referring.
Japan swiftly condemned yesterday's launches, the fourth missile test by the North in less than two weeks.
The previous launches had preceded a state trip to South Korea by Chinese President Xi Jinping and had been read by some analysts as a show of pique at his decision to visit Seoul before Pyongyang.
Statements from Pyongyang have suggested several reasons for the tests, including anger over recent South Korean naval drills near the maritime border.
In between the launches, the North has extended a number of apparent olive branches to the South, including a proposal for both sides to halt all provocative military activity.
Seoul dismissed the offers as "nonsensical" in the light of Pyongyang's nuclear weapons programme.
It was not immediately clear what sort of rockets were fired in the drill KCNA reported today.
