North Korea is particularly sensitive about US-South Korean joint air drills.
A US B-1B strategic bomber was redeployed to the Korean peninsula on Saturday for a joint air drill with South Korea, Seoul's military said, a day after Pyongyang launched an intercontinental ballistic missile.
"South Korea and the US conducted a joint air drill today with the US Air Force's B-1B strategic bomber redeployed on the Korean peninsula," the South Korean Joint Chiefs of Staff said in a statement.
Some of the most advanced jets in the US and South Korean air forces, including the F-35 stealth fighter, also joined the drill, it said.
North Korea is particularly sensitive about US-South Korean joint air drills, experts say, as its air force is one of the weakest links in its military, lacking high-tech jets and properly trained pilots.
While the B-1B no longer carries nuclear weapons, it is described by the US Air Force as "the backbone of America's long-range bomber force" that can strike anywhere in the world.
Since Kim declared North Korea an "irreversible" nuclear state in September, Washington has ramped up regional security cooperation, including its largest-ever joint air exercises with South Korea this month called "Vigilant Storm".
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