SEOUL, South Korea (AP) — North Korea vowed Monday to bolster its nuclear arsenal and gain revenge of a "thousand-fold" against the United States in response to tough U.N. sanctions imposed following its recent intercontinental ballistic missile tests.

The warning came two days after the U.N. Security Council unanimously approved new sanctions to punish North Korea, including a ban on coal and other exports worth over $1 billion. The U.S. ambassador to the U.N., Nikki Haley, called the U.S.-drafted resolution "the single largest economic sanctions package ever leveled against" North Korea.

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