The launch came about two hours after a similar test failed, South Korea's military said, and covered 400 km (250 miles), more than halfway towards the southwest coast of Japan's main island of Honshu.
The launches and earlier nuclear tests show continued defiance of international warnings and a series of U.N. Security Council resolutions and sanctions, which North Korea rejects as an infringement of its sovereignty.
NATO Secretary General Jens Stoltenberg also decried North Korea's "provocative actions".
"I strongly condemn the launch by North Korea of two ballistic missiles," Stoltenberg said in a statement.
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