North Korea said Thursday it had conducted a “tactical nuclear strike” drill that simulated attacks on South Korean military posts, Pyongyang's state-run media reported, as large-scale joint military exercises between Washington and Seoul were set to wrap up the same day.

The drill was aimed at sending a “clear message” to North Korea’s enemies, an official from the Korean Central News Agency reported, citing the General Staff of the Korean People's Army (KPA).

The exercise came after at least one U.S. B-1B heavy bomber joined South Korean fighters for combined air drills above the Korean Peninsula, following joint exercises between two U.S. B-1Bs and Air Self-Defense Force fighter jets over the Sea of Japan.