UNITED NATIONS—North Korea’s foreign minister warned his country would shoot down American warplanes even if they are outside of the country’s airspace, in an escalation Monday of the threat of a military confrontation.

Ri Yong Ho, speaking to reporters in New York, said the U.S. had declared war on North Korea and his country considered all possible responses to be on the table. He cited a Twitter post by President Donald Trump as the basis for saying the U.S. had declared war.

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