Seoul's military said North Korea fired several cruise missiles on Wednesday, in the latest launch that comes as South Korea and the United States hold large joint military drills.
"The South Korean military has detected multiple cruise missiles launched into the East Sea" by North Korea, Seoul's Joint Chiefs of Staff said in a statement, referring to the body of water also known as the Sea of Japan.
"Detailed specifications are being analyzed by South Korea-US intelligence authorities," it added.
After a record-breaking year of weapons tests and growing nuclear threats from Pyongyang, Seoul, and Washington have stepped up security cooperation, and on March 13 began their largest joint military exercise in five years. Known as the Freedom Shield, the exercises last for at least 10 days.
South Korea's military said it would "successfully complete the planned joint Freedom Shield exercise under a firm joint defense stance."
North Korea views all of these exercises as rehearsals for invasion, saying they could be considered a "declaration of war" and has repeatedly threatened "crushing" measures in response.
Wednesday's launch comes about a week after Pyongyang tested its largest and most powerful missile, the Hwasong-17 -- its second ICBM test this year.
North Korean state media described the ICBM launch as a response to the "frantic" exercises between the United States and South Korea.
Pyongyang declared itself an "irreversible" nuclear power last year and leader Kim Jong Un recently called for an "exponential" increase in weapons production, including tactical nuclear weapons.
Kim also ordered the North Korean military this month to step up training in preparation for "real war".