The DPRK's army said in a statement that more than 17,500 U.S. soldiers and 50,000 South Korean troops, plus soldiers from eight other countries and tens of thousands of South Korean paramilitaries, joined in the "war rehearsal".
"No one can vouch that these huge forces concentrated in South Korea will not go over to an actual war action now that the military tensions have reached an extreme pitch on the Korean Peninsula," the statement said.
The United States and South Korea on Monday kicked off their annual Ulchi-Freedom Guardian joint military drill amid high tension on the Korean Peninsula and repeated appeals for restraint on both sides by many countries.
Ulchi-Freedom Guardian is referred to a combined military exercise between the United States and South Korea, which is considered the world's largest computerized command and control operation. The exercise was initiated in 1976 and is held annually during August or September.
The statement said the United States will be "wholly held accountable for the catastrophic consequences to be entailed by such reckless aggressive war maneuvers."