The United States, South Korea and Japan have begun an air and naval exercise off a South Korean island in their latest joint drill condemned by North Korea as a “reckless show of strength.”

Protesters shout slogans during a press conference to oppose the military exercise called Freedom Edge in Seoul, South Korea, Monday, Sept. 15, 2025. A banner reads "Oppose Freedom Edge." (AP Photo/Lee Jin-man)

SEOUL, South Korea (AP) — The United States, South Korea and Japan opened an air and naval exercise off a South Korean island Monday in their latest joint drill condemned by North Korea as a “reckless show of strength.”

The exercise called Freedom Edge is aimed at strengthening the countries’ combined operational capabilities in the sea, air and cyberspace and is necessary to counter North Korea’s growing nuclear and missile threats, South Korea’s Defense Ministry said.

The U.S. Indo-Pacific Command said the exercise will include U.S. Marine and Air Force aerial assets and feature enhanced ballistic-missile and air-defense drills, medical evacuations and maritime operations training, making it “the most advanced demonstration of trilateral defense cooperation to date.”

The exercise off South Korea's southern Jeju Island runs through Friday.

The powerful sister of North Korean leader Kim Jong Un earlier condemned the drills in state media, saying they show the countries’ confrontational stance toward the North.

“The reckless show of strength made by them in real action in the vicinity of the DPRK, which is the wrong place, will inevitably bring bad results to themselves,” Kim Yo Jong said, using the initials of North Korea’s formal name, the Democratic People’s Republic of Korea.

She also criticized the United States and South Korea over their latest Iron Mace tabletop exercise, which aims to explore ways to integrate Washington’s nuclear and South Korea’s conventional capabilities to bolster deterrence against North Korean threats. The U.S. and South Korean militaries did not confirm details of the exercise that was reported to be coinciding with Freedom Edge.

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Protesters shout slogans during a press conference to oppose the military exercise called Freedom Edge in Seoul, South Korea, Monday, Sept. 15, 2025. (AP Photo/Lee Jin-man)

North Korea in the past has carried out its own military demonstrations or weapons tests in response to joint military exercises of its rivals.

Kim Jong Un’s government has repeatedly dismissed calls by Seoul and Washington to restart negotiations aimed at winding down his weapons programs, as he continues to prioritize Russia as part of a foreign policy aimed at expanding ties with nations confronting the United States.

Since Russia’s invasion of Ukraine, Kim has sent thousands of troops and large shipments of weapons, including artillery and ballistic missiles, to help fuel President Vladimir Putin’s warfighting.

Kim also visited China earlier this month, and shared center stage with Chinese President Xi Jinping and Putin at a massive military parade, in another step aimed at strengthening his diplomatic leverage.

A protester holds a sign during a press conference to oppose the military exercise called Freedom Edge in Seoul, South Korea, Monday, Sept. 15, 2025. (AP Photo/Lee Jin-man)