WASHINGTON – A Chinese ship seized an underwater, unmanned U.S. research vessel while American sailors watched, the Pentagon said Friday.

China seized the submarine midday Thursday after pulling alongside the USNS Bowditch, a U.S. oceanographic survey ship, as it was stopped in international waters of the South China Sea, said Navy Capt. Jeff Davis, a Pentagon spokesman. The ship was near the Philippines about 50 nautical miles northwest of Subic Bay when the submarine was seized, Davis said.

The Bowditch was stopped in the water, retrieving two unmanned submarines when a Chinese Dalang III class ship “came alongside of it, put a small boat in the water, went out and seized one of these [unmanned vessels] itself,” Davis said.

“There were multiple attempts made over bridge-to-bridge radio to demand it back,” Davis said. The Chinese ship “acknowledged the communications on bridge-to-bridge radio. It wasn’t a radio problem. But ignored the request for it to be returned and took it.”

"The Department of Defense has called upon China to immediately return" the seized vessel, Pentagon Press Secretary Peter Cook said in a statement.

The Bowditch did not have uniformed U.S. personnel on it and the Defense Department civilians on board are assigned to Military Sealift Command. While the seized submarine was unmanned, it “still retains the protections under international law as a sovereign, immune vessel of the United States of America,” Davis said.

The information that the Bowditch’s underwater vessels collect includes water salinity, temperature and other data that is used to assist in Navy sonar communications, he said.

The Bowditch had made a port call to the Philippines in recent days, Davis said. The seized vessel, he said, is something that could be purchased on the commercial market for approximately $150,000 and had no classified systems on it.

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