SEOUL—North Korean leader Kim Jong Un described the results of the country’s successful launch its second ballistic missile in a little more than a week as “perfect,” as Pyongyang increases the pace of its testing in its quest to develop the ability to strike the continental U.S. with a nuclear-tipped weapon.

North Korea fired the missile from the Pukchang airfield, about 40 miles north of the capital, Pyongyang, at about 4:30 p.m. Sunday local time, according to the U.S. Pacific Command and South Korea’s Ministry of Defense.

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