"The US, with its dangerous military provocation, is pushing the risk of a nuclear war on the peninsula to a tipping point," it said, describing the peninsula as the "world's biggest tinderbox."
During Saturday's drill, long-range B-1B Lancer bombers reportedly flew close to the heavily-fortified border between two Koreas and dropped 900 kilogramme bombs.
Pyongyang described the joint drill as a "dangerous military gambit of warmongers who are trying to ignite the fuse of a nuclear war on the peninsula."
"A small misjudgment or error can immediately lead to the beginning of a nuclear war, which will inevitably lead to another world war," it said.
Tension has been high as the US administration under President Donald Trump and the North's regime under leader Kim Jong-Un have exchanged hostile rhetoric for months.
Tension further escalated after Tuesday's ICBM test, a milestone in the North's decades-long quest for weapons capable of reaching the US.
The impoverished, isolated country has staged five nuclear tests - including two last year - and has made a significant progress in its missile capability under Kim, who took power in 2011.
In another drill held after the ICBM test, US and South Korean troops fired ballistic missiles simulating an attack on the North's leadership "as a strong message of warning," the South's military said at the time.
The US Missile Defense Agency said last week it would soon test an anti-ballistic missile system in Alaska.
- Telegraph UK