North Korea fired multiple ballistic missiles off the country's east coast on Monday morning, one day after the U.S. held joint military drills with South Korea and Japan.
Kim Yo Jong, North Korean leader Kim Jong Un's sister, called the U.S. "the worst maniacs" in a statement after the latest missile launches.
"The frequency of using the Pacific as our firing range depends upon the U.S. forces’ action character," Kim Yo Jong said in a statement distributed by state media. "We are well aware of the movement of U.S. forces’ strategic strike means recently getting brisk around the Korean Peninsula."
South Korea and Japan both detected ballistic missile launches on Monday morning, though the types of missiles and their flight paths were not immediately known.
On Saturday, North Korea launched a Hwasong-15 intercontinental ballistic missile in what state media said was a test to verify the country's "fatal" nuclear attack capacity.
The ICBM flew a distance of about 615 miles and reached an altitude of 3,585 miles before landing in waters off the coast of Japan.
The U.S. flew long-range supersonic bombers on Sunday in reaction to that Saturday test, with South Korean fighter jets escorting American B-1B bombers.
North Korea launched a record 90 missiles last year, though Saturday's ICBM test was the first launch since Jan. 1.
The Associated Press contributed to this report.