China has been building a series of surveillance platforms spanning parts of the South China Sea. Many of the radars are floating in Chinese water but some are in international waters. Associate Fellow at the Asia-Pacific Programme at Chatham House Bill Hayton told Express.co.uk: "Over the past few years, China has put in place a whole load of systems; satellite, radar, and underwater systems to try and observe what's going on in the South China Sea.
"Obviously they built these seven new artificial islands on coral reefs in the Spratly Islands and that adds to other things they've built elsewhere.
"This allows them to send ships whether they be Navy or coastguard ships or militia to stop things they don't like.
"For example, to stop other countries fishing or monitor warships from other countries passing through."
It comes as satellite imagery service Orion mapped the surveillance gear which they say "reinforces China’s strategic advantage over other countries in the region, and can be used to monitor US Navy movements".
Research by CSIS Asian Maritime Transparency Initiative found that the surveillance platforms are part of China's "Blue Ocean Information Network".
The platforms are installed with electro-optical/infrared sensor turrets, high-frequency radio and cellular masts, according to Forbes.
Situated close to the Paracel and Spratly Island, they will increase China's radar coverage of the South China Sea.
China currently monitors vessels with multiple sensors deployed at depths of up to 2,000 meters below sea level named the "Underwater Great Wall".
The Philippine foreign ministry said the incident happened three months ago at the Scarborough Shoal, a prime fishing site seized by Beijing in 2012 after a standoff that prompted an unprecedented international legal challenge by Manila.
In a statement, it gave no other details about that incident, but it also protested China's "continuing illicit issuances of radio challenges to Philippine aircraft conducting legitimate regular maritime patrols."