An aerial view of Taiping island, in the South China Sea.

A Chinese Navy warship has seized an underwater drone deployed by an American oceanographic vessel in international waters in the South China Sea, triggering a formal demarche from the United States and a demand for its return, a US defense official said on Friday.

The incident – the first of its kind in recent memory – took place on Dec. 15 northwest of Subic Bay just as the USNS Bowditch, an oceanographic survey ship, was about to retrieve the unmanned, underwater vehicle (UUV), the official said, speaking on condition of anonymity.

“It was taken” by China, the official said, adding the craft was seized in international waters about 50 miles off Subic Bay.

The “naval glider” was used to test water salinity and temperatures to help in the mapping of underwater channels, the official said.

While the probe was a US Navy vessel, it was operated by civilians, the official said.

The vessel’s seizure comes amid continued tensions in the South China Sea.

[vuukle]