North Korea fired about 10 artillery shells from its 240mm multiple rocket launcher system toward the Yellow Sea on Thursday morning, just a day after South Korea held joint aerial drills with the United States and Japan.

According to South Korea’s military, the shells were launched around 10 a.m. from the Sunan area near Pyongyang. Intelligence agencies from South Korea and the US are currently analyzing the launch, which is seen as a response to the recent trilateral air exercises.

The joint drills, conducted on Wednesday, featured South Korea’s F-15K, the US F-16, and Japan’s F-2 fighter jets, marking the first trilateral exercise under South Korean President Lee Jae Myung’s administration. The exercise was aimed at strengthening coordination among the three allies in response to North Korea’s growing military provocations.

The 240mm launcher used by the North is capable of targeting Seoul and nearby regions, raising concerns in the South. Last year, Pyongyang claimed to have tested an upgraded version of this launcher with advanced guidance systems.

Thursday’s launch follows a series of provocative tests by North Korea, including cruise missile launches toward the East Sea last month and multiple short-range ballistic missile tests on May 8. These activities come amid heightened regional tension following a failed launch of a North Korean naval destroyer, which leader Kim Jong-un condemned as a “criminal act.”

South Korea’s Joint Chiefs of Staff (JCS) warned that they are maintaining full readiness and monitoring closely to deter any potential misjudgment by North Korea. The JCS reaffirmed the South’s ability to respond “overwhelmingly” to any future provocations.