SEOUL, South Korea — North Korea used multiple-rocket launchers off its east coast on Saturday to fire three short-range missiles that could strike United States military bases deep in South Korea, officials in Seoul said.

The launches were the North’s first rocket tests since two intercontinental ballistic missile, or ICBM, were fired last month. By resuming the tests, North Korea defied repeated urgings from the United States and South Korea to stop weapons trials and other provocations to pave the way for dialogue.

The United States Pacific Command said that one of the three ballistic missiles had blown up immediately after blastoff, but that two others had traveled about 155 miles before splashing down.

That would be far enough to reach major South Korean and American military bases, including those near the city of Pyeongtaek, about 60 miles south of Seoul. The range would also be sufficient to reach Seongju, a South Korean town where the United States has begun installing an advanced missile-defense system known as Thaad.