South Korea and the United States fired eight ballistic missiles on Monday in response to North Korean weapons tests the previous day, Seoul's military said.
The Joint Chiefs of Staff said the allies launched the ground-to-ground Army Tactical Missile System (ATACMS) missile at targets in the East Sea, also known as the Sea of Japan, in the early morning.
The 10-minute volley comes a day after North Korea launched eight short-range ballistic missiles following a South Korea-US joint military exercise involving a US aircraft carrier.
"Our military strongly condemns the North's series of ballistic missile provocations and sternly urges it to immediately stop acts that raise military tensions on the peninsula," it added.
Monday's launches mark the second such joint show of force by the allies under South Korea's hawkish new President Yoon Suk-yeol, who has vowed a tougher stance against Pyongyang.
"Our government will respond decisively and sternly to any provocations from North Korea," Yoon said Monday during a speech commemorating Memorial Day.
Last month, Seoul and Washington carried out combined launches after Pyongyang fired three ballistic missiles -- including a suspected intercontinental ballistic missile -- in their first such joint move since 2017.
Pyongyang has doubled down on upgrading its weapons programme, despite facing crippling economic sanctions, with officials and analysts warning that the regime is preparing to carry out a fresh nuclear test.
The regime has carried out a blitz of sanctions-busting weapons tests this year, including firing an intercontinental ballistic missile (ICBM) at full range.