North Korea says it launched two tactical ballistic missiles on Monday to simulate a nuclear air explosion.
Tuesday's edition of the ruling Workers' Party newspaper, Rodong Sinmun, said a missile unit fired the ground-to-ground ballistic missiles from Pyongyang.
It said their mock nuclear warheads were detonated 500 meters above a target islet in the country's northeast.
South Korea's military has said the North launched two short-range ballistic missiles from near Pyongyang on Monday morning.
The Rodong Sinmun also said the country completed a three-day test of an "underwater nuclear attack drone" on Monday.
It said the "Haeil-1" set off from Wonsan in the east on Saturday and cruised along a course simulating a distance of over 600 kilometers.
The drone reportedly detonated its warhead in waters off a northeastern province after more than 41 hours.
North Korea's moves come as the United States is deploying a nuclear-powered aircraft carrier near the Korean Peninsula, as part of joint drills with South Korea.