North Korea fired a pair of medium-range ballistic missiles from its east coast into the Sea of Japan at about 6 a.m. local time, according to South Korea's military. The first missile flew about 500 miles.

This follows the launch of two short-range missiles last week. A senior defense department official says neither missile was a threat to the U.S. or regional allies, but that the launches violate multiple United Nations Security Council resolutions.

"We call again on North Korea to refrain from actions that further raise tensions in the region and focus instead on taking concrete steps toward fulfilling its international commitments and obligations," State Department spokesman John Kirby said, in a statement.

The shows of military strength by the North come as 17,000 U.S. troops and 300,000 South Korean soldiers take part in annual war games that the U.S. maintains are defensive in nature. North Korea objects to the exercises with antagonistic rhetoric and threats each year.

Relations are particularly sour between North and South this year, following the North's fourth U.N.-rules-breaking nuclear test and a rocket launch widely viewed to be a ballistic missile test. South Korea shuttered the joint North-South Kaesong industrial complex last month as a unilateral reaction to the North's nuclear test. That came just before the international community slapped a new package of strict sanctions on North Korea through a United Nations Security Council resolution.

The drumbeat of North Korean shows of military strength and rhetoric will likely continue in the lead-up to May, when the North's Workers Party Congress meets for the first time since 1980.

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