Beijing said Hanoi's accusation of China jeopardizing regional air safety by conducting test flights on a South China Sea reef was "indefensible".

China's Flight Inspection Center of Civil Aviation Administration had already reported technical information such as the flight plan and route to aviation authorities of the Ho Chi Minh City Flight Information Region on Dec 28 according to international practice, said Foreign Ministry spokesperson Hong Lei on Monday.

However, we still have received no feedback until now, Hong said.

According to media reports on Saturday, the Civil Aviation Authority of Vietnam (CAAV) had filed a complaint with the United Nations' International Civil Aviation Organization, or ICAO, and sent a protest letter to China's government, objecting to China's flight test on a newly-built airport on a South China Sea reef known as Yongshu Jiao.

Lai Xuan Thanh, director of the CAAV said: "Chinese aircraft have ignored all the rules and norms of the ICAO by not providing any flight plans or maintaining radio contact with Vietnam's air traffic control center."

But Hong disclosed that besides other procedures, China also tried technical communication and explanation through diplomatic channels with Vietnam on Dec 30, but the Vietnamese side continued to obstruct China's test regardless of the fact that it was conducted for civil use and international public welfare.

"The Chinese government then decided to change the flight test into a state aviation activity and hired a civil aircraft to complete related tests," Hong said, indicating that the test would not be restricted by the International Convention on Civil Aviation or other ICAO provisions.

The result of the test showed that the airport of Yongshu Jiao met civil aviation standards and is capable of providing public services such as emergency relief, maritime search and rescue, Hong added.