Manila (AFP) - The Philippines said Monday it would install a civilian flight-tracking system in the disputed South China Sea after China landed several aircraft on one of its man-made islands in the potential flashpoint region.

The automatic dependent surveillance-broadcast (ADS-B) machine, which detects aircraft positions using satellite signals, will be operational by November on Pagasa island, the biggest Filipino-occupied feature in the disputed Spratlys, said Rodante Joya, acting director of the Civil Aviation Authority of the Philippines (CAAP).

An average of 200 civilian flights pass over the Spratlys daily, Joya told AFP, adding the Pagasa surveillance system was part of a broader 10-billion-peso ($209 million) effort to expand the country's commercial flight radar coverage to 80 percent from the current 30 percent.

"Our objective is to track all commercial flights passing over our airspace," Joya said, adding the radars would not be used to monitor military aircraft.

China has built massive structures over South China Sea reefs claimed by the Philippines, Vietnam, Brunei and Taiwan, including a 3,000-metre (9,842-foot) runway on Fiery Cross reef.

The Philippines has expressed concern that China's test landings on Fiery Cross reef earlier this month would lay the groundwork for the declaration of an air defence identification zone (ADIZ) similar to the one Beijing claimed over the East China Sea in 2013 that riled Japan.

Joya said a CAAP plane received a radio message as it was about to land on Pagasa island on January 6, warning against landing in "Chinese territory".

The message, which was in English, appeared to have been taped, he said. The Filipino crew ignored the message and proceeded to land and survey the site for the plane-tracking ADS-B machine.

Presidential spokesman Herminio Coloma told reporters the Philippine foreign affairs department has been informed of the incident.

The Philippines has asked a United Nations-backed tribunal to declare China's sea claims as invalid and expects a decision early this year.

Philippines plans flight-tracking system in disputed sea