South Korea and the United States fired eight ballistic missiles into the Sea of Japan on Monday in response to North Korea's missile launches the previous day.
The allies launched the ground-to-ground Army Tactical Missile System projectiles from around 4:45 a.m. following North Korea's launches of eight short-range ballistic missiles, according to the Joint Chiefs of Staff of the South Korean military.
"Our government will respond firmly and sternly to any North Korean provocation," South Korean President Yoon Suk Yeol said, according to Yonhap News Agency.
"Even at this moment, North Korea's nuclear and missile threats are getting sophisticated," Yoon was quoted by Yonhap as saying amid signs Pyongyang is preparing to conduct what would be its seventh nuclear test and first since 2017.
"North Korea's nuclear and missile programs are reaching the level of threatening not only peace on the Korean Peninsula but also in Northeast Asia and the world," he said.
According to U.S. Forces Korea, the combined live-fire exercise involved one U.S. Army missile and seven South Korean missiles.
"To demonstrate the ability of the combined U.S.-ROK force to respond quickly to crisis events, U.S. Forces Korea and Republic of Korea militaries conducted a combined live-fire exercise," the USFK said in a statement.
The Republic of Korea is the formal name of South Korea.
"The ROK-U.S. alliance remains committed to peace and prosperity on the Korean Peninsula and throughout the Indo-Pacific," it said.
On Monday morning, North Korea's state-run Korean Central News Agency and the Rodong Sinmun, the official newspaper of the Workers' Party of Korea, did not carry any reports about Sunday's missile firings, marking the fifth consecutive time that Pyongyang has remained silent about missile launches.
North Korea has fired a series of projectiles, including an intercontinental ballistic missile and two other missiles on May 25 just after U.S. President Joe Biden ended a trip to South Korea and Japan.