China rejects Vietnam protest over sea flight test

China rejected a protest from Vietnam over a flight test it has conducted on a new airstrip on a man-made island in the South China Sea, saying it is part of China's territory.

The Chinese Foreign Ministry said Saturday it conducted a civil flight test on the newly built airstrip on Fiery Cross Reef in the Spratly Islands, a chain of islets rich in natural resources that are the focal point of rival claims by neighboring governments.

China has become more assertive in pressing its claims in the South China Sea, and has recently piled sand on coral reefs atop of which it built airfields, radar installations and docking facilities. As with most of its policy in the South China Sea, Beijing has remained opaque about its plans for the island airstrips.

Foreign Ministry spokeswoman Hua Chunying said the test flight was to find out if the new airfield met the standards for civil aviation.

"Relevant activity falls completely within China's sovereignty," Hua said. "The Chinese side will not accept the unfounded accusations from the Vietnamese side."

China insists its island building works are justified and don't constitute a threat to stability and freedom of navigation. The U.S. and its regional allies have expressed concern that China's robust assertion of its claims has aggravated tensions.

Although Vietnam already has an airstrip in the Spratlys, it is just long enough to accommodate slow-moving cargo and surveillance planes. China's airstrip on Fiery Cross Reef is long enough for bombers capable of launching cruise missiles.