China to return US drone

China will return an underwater US drone seized by a naval vessel this week in the South China Sea, both countries said on Saturday, but Beijing complained that Washington had been "hyping up" the incident.

The drone, known as an unmanned underwater vehicle (UUV), was taken on Thursday, the first seizure of its kind in recent memory. The Pentagon went public with its complaint after the action and said on Saturday it had secured a deal to get the drone back.

"Through direct engagement with Chinese authorities, we have secured an understanding that the Chinese will return the UUV to the United States," Pentagon spokesman Peter Cook said in a statement.

The drone, which the Pentagon said was operating lawfully was collecting data about the salinity, temperature and clarity of the water about 50 nautical miles northwest of Subic Bay, off the Philippines.

It was seized just as the USNS Bowditch was about to retrieve it, US officials said.

China's Defense Ministry said a Chinese naval vessel discovered a piece of "unidentified equipment" and checked it to prevent any navigational safety issues before discovering it was a US drone.

"China decided to return it to the US side in an appropriate manner, and China and the US have all along been in communication about it," the ministry said on its website.

"During this process, the US side's unilateral and open hyping up is inappropriate, and is not beneficial to the smooth resolution of this issue. We express regret at this," it added.

The drone incident has raised fresh concerns about China's increased military presence and aggressive posture in the energy-rich South China Sea, through which about $5 trillion in trade is shipped every year. Brunei, Malaysia, the Philippines, Taiwan and Vietnam also have claims to the waterway.

New satellite imagery shows China has installed weapons, including anti-aircraft and anti-missile systems, on all seven artificial islands it has built in the South China Sea, a US research group said this week.