SEOUL/TOKYO - North Korea fired what is believed to have been an intermediate-range ballistic missile toward the Sea of Japan on Sunday, marking its first such activity of the year and coming less than a month after it launched a solid-fuel intercontinental ballistic missile, the South Korean military said.

The military said one missile was fired at around 2:55 p.m. from near Pyongyang and, after flying about a thousand kilometers, fell into the sea. The Japanese government confirmed that the projectile fell outside Japan's exclusive economic zone.

The launch came as tensions remain high on the Korean Peninsula, with the North recently firing a barrage of artillery shells near the disputed western maritime boundary with South Korea and Seoul conducting a military exercise in retaliation.

No damage to aircraft or vessels has been reported, Japan said.

North Korean leader Kim Jong Un last week called South Korea his nation's "principal enemy" and the state that is "most hostile" toward Pyongyang, according to the country's official media.

Japan's Defense Ministry only confirmed that Sunday's ballistic missile flew a distance of at least 500 km at a maximum altitude of over 50 km.

An intermediate-range class ballistic missile can reach the U.S. territory of Guam, where key military bases are located.

Japan lodged a stern protest with North Korea over the latest missile launch, calling it a violation of U.N. Security Council resolutions against it and condemning the action as threatening the safety of Japan, according to the ministry.

North Korea last launched a ballistic missile on Dec. 18 toward the Sea of Japan, with the missile fired at a lofted angle.

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