The launch takes place days before the US vice president visits the region
North Korea has test-fired a short-range ballistic missile ahead of US Vice President Kamala Harris' trip to the region, Seoul says.
The projectile, launched from around Taechon in North Korea's northwest, traveled around 600km (373 miles) before landing in the Sea of Japan, the South Korean Joint Chiefs of Staff (JCS) said.
The news comes ahead of Harris' visit to South Korea and Japan, and the planned US-South Korean joint naval exercise. The VP will embark on an Asian tour next week.
South Korea's presidential National Security Council said the launch was illegal under international law.
JCS Chairman General Kim Seung-kyum and General Paul LaCamera, the commander of the South Korea-US Combined Forces Command, released a statement vowing to "further solidify a combined defense posture against any North Korean threats and provocations." They added that the North's weapon tests undermine peace.
The US Indo-Pacific Command separately stated that Washington's commitments to defend South Korea and Japan "remain ironclad."
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The USS Ronald Reagan aircraft carrier docked at South Korea's port of Busan for the first time in nearly five years on Friday. Two US guided missile destroyers also arrived in Busan, while another destroyer docked near Changwon as part of the strike group's visit.
The US and South Korea resumed large-scale joint drills last month after several years of hiatus. Pyongyang considers the exercises a threat to national security.