The incident occurred near Scarborough Shoal, one of two hotly disputed areas where confrontations between the two countries have flared since last year.
Manila protested Beijing's ship movements Thursday after its military monitored more than 200 Chinese vessels over the past three months in disputed waters.
The platform appears to be topped with a radome and solar panels, and its strategic location makes it likely it is intended to extend China’s radar or signals intelligence collection in the area.
The arrival of the carrier Ronald Reagan and its strike group in the Asian financial hub is being seen as a friendly gesture ahead of a planned meeting later this month between President Donald Trump and Chinese leader Xi Jinping.
The Coast Guard has declared the lighthouses to be "excess," so the government will try to turn their operation over to a nonprofit group or government agency.
The barren shoal is on the eastern edge of the disputed Spratly archipelago where tensions have run high in recent years after China built seven disputed reefs into man-made islands and reportedly installed missile defense systems.
A Philippine navy frigate has run aground on a shoal in the disputed South China Sea and efforts are underway to retrieve it and its crew who were unhurt.