South Korea and the United States fired four ground-to-ground missiles into the East Sea, more commonly known as the Sea of Japan, the Yonhap news agency said Wednesday, citing South Korea's military.
The launches were in response to North Korea firing a ballistic missile over Japan for the first time in five years on Tuesday, the South Korean military said.
South Korea and the United States each fired two Army Tactical Missile System (ATACMS) missiles, which hit mock targets, the South Korean Joint Chiefs of Staff said.
South Korean President Yoon Suk-yeol called the North Korean launch a "provocation", and vowed a "stern response".
On Tuesday, South Korean and US fighter jets had carried out a bombing drill at a target in the Yellow Sea.
The last time Pyongyang fired a missile over Japan was in 2017, at the height of a period of "fire and fury" when North Korean leader Kim Jong Un traded insults with then-president Donald Trump of the United States.
United Nations chief Antonio Guterres condemned North Korea's latest test as "clearly an escalation", while US President Joe Biden and Japanese Prime Minister Fumio Kishida decried it "in the strongest terms".