A U.S. Navy warship sailed close to a disputed island in the South China Sea on Saturday, challenging maritime claims by China, Taiwan and Vietnam.

The trip near Triton Island, first reported by the Wall Street Journal, is what the Pentagon calls a "freedom of navigation operation."

The guided missile destroyer USS Curtis Wilbur traveled within 12 nautical miles of Triton Island in the Paracel Islands, which are claimed by China, Taiwan and Vietnam. The trip was an "innocent passage," the Pentagon said, which under international law is permitted through territorial waters — which can extend no further than 12 nautical miles from a state's shores.

The U.S. doesn't take a position on the territorial disputes over the island. But it says attempts by all three claiming parties to regulate passage through those waters, by requiring permission or advance notification, violate international law.

On Saturday, "no claimants were notified prior to the transit, which is consistent with our normal process and international law," the Pentagon said in a statement.

"The Pentagon adds that no Chinese military vessels were in the area," NPR's Anthony Kuhn reported for our Newscast division. "But China's defense ministry says in a statement that it warned the U.S. ship before chasing it away."

"The ministry criticized the move as illegal, provocative and unprofessional," Anthony says.

The U.S. conducted similar operations last October in the Spratly islands, near the Philipines, Anthony says. The Spratlys are claimed by China, Taiwan, Vietnam, Malaysia, the Philippines and Brunei.

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